They are meetings that can define moments in history and shape the future of the world.
From the Second World War to the Cold War, summits between the US and Russia have carried a weight that other political events rarely match.
But while past leaders have often been tackling an external threat, US President Donald Trump goes into Friday’s meeting with Vladimir Putin fighting a war at home – in particular, the investigations into his campaign’s ties with Russia.
Mr Trump has said he wants to find ways to work with Mr Putin, a goal made more difficult by sharp differences over Russia’s actions in Syria and Ukraine, and allegations that Moscow meddled in the 2016 US presidential election.
Here is a look back at past meetings between US and Russian leaders, ranging from openly hostile exchanges to diplomatic breakthroughs.
Joseph Stalin and Theodore Roosevelt, 1943
Held at the Soviet embassy in Tehran, this meeting was held against the backdrop of World War II. Winston Churchill also attended the summit and the three leaders discussed the opening of a second front in western Europe
The fact that the nations were allies did not mean Russia was not suspicious. During the summit, Stalin observed Roosevelt passing a handwritten note to Churchill, and instructed his head of intelligence in Persia, Ivan Ivanovich Agayants, to get hold of a copy. He succeeded. It read: “Sir, your fly is open.”
The meeting is perhaps most famous for almost seeing the trio assassinated. Gevork Vartanyan, a Soviet agent, played a key role in stopping Germany’s master spy, Otto Skorzeny, from blow up the summit.
Stalin and Roosevelt established a genuine rapport at the summit and the Russian leader was portrayed favourably at the time by the US media.
Dwight D. Eisenhower and Nikita Khrushchev, 1959
This was the first visit by a Soviet leader to the United States and the two men came to general agreement on a number of issues, generating optimism for improved relations.
A joint communique from the September meeting suggested that both “agreed that these discussions have been useful in clarifying each other’s position on a number of subjects” and they hopes it would lead to a “just and lasting peace”.
Those hopes were later dashed when the Soviets shot down an American U-2 spy plane over Russia and captured the pilot in May 1960 – an incident dramatised in the recent Hollywood film Bridge of Spies.
John F. Kennedy and Khrushchev, 1961
This has been called “the most ill-judged summit of the Cold War”. The two leaders met each other in Vienna just as the Cold War was raging around them.
Kennedy approached the Soviet leader via a letter during his transition to the White House, hoping for real progress on a Nuclear Test Ban Treaty.
However, the pair clashed over Berlin, with JFK refusing to recognise East German sovereignty over the city. Kennedy warned of a “cold winter” ahead and a few months later the Soviet Union began building the Berlin Wall.
Kennedy later said the Khrushchev meeting was the “worst thing in my life. He savaged me.”
“If the US wants to start a war over Germany let it be so,” Khrushchev reportedly said.
Lyndon B. Johnson and Alexei Kosygin, 1967
Johnson and Kosygin met at the state college campus of Glassboro, a venue described in the world’s press at the time as “that sleepy little town”.
“The place looked like a military command centre,” Marius Livingston, a history professor at the college, told the New York Times. “What was once a tranquil retreat was suddenly the center of the world’s attention.”
The summit was held against the backdrop of the Israeli-Arab Six Days War and the Vietnam War. Although Johnson and Kosygin failed to reach agreement on anything significant, the generally amicable atmosphere of the summit was referred to as the “Spirit of Glassboro” and was seen to have improved Soviet–US relations.
Brezhnev and Nixon, 1972
Nuclear weapons topped the agenda of this summit, at which they signed a historic agreement setting limits to the nuclear arsenals of the two super-powers.
They also set up a hotline to prevent a nuclear war breaking out by accident.
“It is an enormously important agreement,” Mr Nixon said at the time. “But, again, it is only an indication of what can happen in the future as we work towards peace in the world. I have great hopes on that score.”
The pair forged a successful working relationship but they wouldn’t have much time to achieve anything else – Nixon resigned in disgrace over the Watergate scandal two years later.
Gorbachev and Reagan, 1987
This summit saw a genuine reset of US-Soviet relations and is still seen as one of the most famous US-Russian encounters ever.
A year earlier, the pair had paved the way at the Reykjavik Summit, agreeing in principle on the need to reduce their nuclear arsenals. But a possible accord foundered at that meeting over Soviet insistence that the United States scrap its space-based missile-defence plans.
In December 1987, the leaders signed the Intermediate-range Nuclear Forces (INF) Treaty in a first attempt to reverse the nuclear arms race.
Mr Reagan described it at the time as the realisation of “an impossible vision”.
The pair developed a strong working relationship, partly thanks to the seal of approval from Margaret Thatcher, who, after meeting Mikhail Gorbachev three years earlier had declared: “I like Mr Gorbachev. We can do business together.”
Boris Yeltsin and Bill Clinton, 1993
It is hard to believe now – amid allegations that Russia meddled in the 2016 presidential election – that after the first meeting between Yeltsin and Clinton they issued a joint declaration calling for the promotion of democracy.
Clinton promised Yeltsin strong support in the form of financial assistance to promote various programmes, including funds to stabilise the economy, to house decommissioned military officers, and to employ nuclear scientists.
“As long as there is President Yeltsin in power in Russia,” Mr. Yeltsin said on his arrival, “then definitely the reforms will continue.”
The two developed a genuine rapport and Yeltsin met Clinton in Washington two years later. The visit included some colourful moments, as Clinton revealed many years later.
According to the former president, Yeltsin got so drunk during the presidential visit that he was found standing outside the White House in his underpants, trying to hail a taxi so he could go out for a pizza.
The following night, a guard mistook him for an intruder after the former Russian president was discovered stumbling drunkenly around the basement of the official visitor’s residence.
Vladimir Putin and George W Bush, 2001
Soon after President George W. Bush’s inauguration, Putin met with him in Slovenia in June 2001. While nothing concrete was established, it became famous for Mr Bush’s personal thoughts of his Russian counterpart. Asked what he thought of Russia new leader, Bush replied: ”I looked the man in the eye. I found him to be very straightforward and trustworthy. We had a very good dialogue. I was able to get a sense of his soul.”
His sentiments were met with scepticism at home. ”I don’t trust Mr. Putin,” Senator Joe Biden said at the time. “Hopefully the president was being stylistic rather than substantive.”
Despite the warmth shown at the outset, relations cooled significantly over the years. The US invasion of Iraq in 2003, which Russia criticised, marked a turning point and ties began to sour. Putin believed the 2004 Orange Revolution in Ukraine was the result of a CIA plot. The tensions kept boiling and a brief war between Russia and Georgia in 2008 led to a freeze in Russia-U.S. relations.
Barack Obama and Dmitri Medvedev in 2009
This Moscow summit was seen as the start of a new chapter in Russian-American relations.
Mr Obama and Mr Medvedev pledged they were on the path to “reset” US-Russian ties, announcing agreements on nuclear arms treaties and future work on missile defence.
“We resolve to reset US-Russian relations so that we can cooperate more effectively in areas of common interest,” Obama said at a press conference with Medvedev in the Kremlin.
“Today we’ve made meaningful progress and demonstrated through means and words what a more constructive US Russian relationship can look like in the 21st century,” Obama added.
It didn’t last long though. Mr Obama had focused on building warm ties with Putin’s ally, Mr Medvedev. When Medvedev stepped down in 2012 to let his mentor reclaim the top job, Mr Putin accused the US of fomenting mass protests in Moscow against his return to the presidency
Obama v Putin, 2016
This meeting, held on the sidelines of the G20 summit in Hangzhou, China, was described by Mr Obama as “candid, blunt and businesslike”.
Photographs suggested that the exchange between two of the most powerful men in the world had been frosty, and Mr Obama said afterwards that “gaps of trust” between the rival powers had hindered negotiations.
In comments that would later take on greater significance in light of the hacking accusations levelled at Moscow over the US election, Mr Obama expressed concerns to Mr Putin about cybersecurity issues.
He urged Mr Putin not to let cyberspace become the “wild, wild west” and issued a stark warning that America had “more capacity than anybody, both offensively and defensively”.