US President Donald Trump pressed Vladimir Putin at their first meeting today about Russian interference in the 2016 presidential election, US Secretary of State Rex Tillerson said.
The Russian president has denied any meddling in the US democratic process last year and Moscow has asked for proof that it took place.
Mr Trump promised a rapprochement with Moscow during his campaign for the presidency last year. But he has been unable to deliver on that pledge because his administration has been dogged by investigations into the allegations of Russian interference in the election and ties between his campaign and Moscow. Mr Trump said his team did not collude with Russia.
Speaking on the sidelines of the G20 summit in Hamburg, Mr Tillerson said the two leaders "had a very robust and lengthy exchange on the subject. The president pressed President Putin on more than one occasion regarding Russian involvement".
"The two leaders agreed that this is a substantial hindrance in the ability of us to move the Russian-US relationship forward," Mr Tillerson told reporters.
The two leaders agreed to work on commitments of "non-interference in the affairs of the United States and our democratic process as well as those in other countries", he added.
The face-to-face encounter was one of the most eagerly anticipated meetings between two leaders in years.
Mr Putin and Mr Trump agreed on a ceasefire in south western Syria during the talks, Russia's Foreign Minister Sergei Lavrov has said.
The truce would start on Sunday, Mr Lavrov told reporters.
The Russian and US leaders had also agreed to work on solving the Ukrainian crisis, and a US representative would visit Russia for consultations on the issue, Mr Lavrov added.
Mr Trump and Mr Putin spoke through translators with their respective foreign ministers present for six minutes before reporters were allowed into the room for their statements. Afterwards the reporters were ushered out and the meeting continued.
"President Putin and I have been discussing various things, and I think it's going very well," Mr Trump told reporters, sitting alongside the Russian leader.
"We've had some very, very good talks. We're going to have a talk now and obviously that will continue. We look forward to a lot of very positive things happening for Russia, for the United States and for everybody concerned. And it's an honour to be with you."
Mr Putin, through a translator, said: "We spoke over the phone with you several times," adding: "A phone conversation is never enough."
"I am delighted to be able to meet you personally, Mr President," he said, noting that he hoped the meeting would yield results.
Both men sat with legs splayed. Mr Trump listened intently as Mr Putin spoke.
The meeting lasted more than two hours and US first lady Melania Trump came in at one point to urge them to conclude, Mr Tillerson said.
Before the meeting, some feared the Republican president, a political novice whose team is still developing its Russia policy, would be less prepared for the talks than Mr Putin, a former KGB agent who has dealt with the last two US presidents and scores of other world leaders.
Amid criticism of Russia's actions in Ukraine and Syria and the investigations into its role in the US campaign, Mr Trump has come under growing pressure to take a hard line against the Kremlin.
Yesterday, Mr Trump delivered some of his sharpest remarks about Moscow since becoming president, urging Russia to stop its "destabilising activities" and end its support for Syria and Iran.
But Mr Trump stopped short yesterday of any personal criticism of Mr Putin and declined to say definitively whether he believed US intelligence officials' assertion that Russia had interfered in the 2016 US election.
"I think it was Russia but I think it was probably other people and/or countries, and I see nothing wrong with that statement. Nobody really knows. Nobody really knows for sure," Mr Trump said on a visit to Poland.