U.S. national security adviser John Bolton is due to arrive in Moscow for talks with Russian Foreign Minister Sergei Lavrov amid expectations he will lay the ground for a July summit between President Donald Trump and his Russian counterpart, Vladimir Putin.
Bolton is due to hold a news conference at 1630 GMT/UTC after his meetings, where he might announce the date and location of a summit.
Bolton is heading to Moscow after meetings with U.S. allies on June 25-26 in London and Rome.
U.S. Secretary of State Mike Pompeo said in a television interview over the weekend that Trump is likely to meet Putin "in the not-too-distant future."
The summit is expected around the second half of July after Trump attends a NATO summit in Brussels on July 11-12 and then visit Britain on July 13. It is unclear where it would be held. Vienna and Helsinki were cited as possible venues.
An Austrian newspaper earlier this week said teams from the United States and Russia were already in Vienna preparing for a July 15 meeting between the two leaders.
However, a senior U.S. official, speaking on condition of anonymity, told Reuters on June 26 that Finland's capital, Helsinki, was the likeliest choice, but the final decision depended on the outcome of talks Bolton is having with the Russians.
Trump and Putin have met twice on the sidelines of international summits and they have spoken at least eight times by telephone.
Trump telephoned Putin to congratulate him in March after the Russian president's reelection and said the two would meet soon.
However, Russian officials have since complained about the difficulty of setting up such a meeting, as ties between Washington and Moscow have further deteriorated over the conflict in Syria and the poisoning of a former Russian spy in Britain, which the West blames on Moscow.
Relations were already severely strained by tension over issues including Russia's seizure of Crimea, its role in wars in Syria and eastern Ukraine, and what U.S. intelligence agencies have concluded was an "influence campaign" ordered by Putin in an attempt to affect the U.S. presidential election, in part by bolstering Trump and discrediting his Democratic rival, Hillary Clinton.
Democrats and some Republicans have accused Trump of being soft on Russia. Trump made clear during his campaign and into his presidency that he wants better relations with Russia and Putin, and has often praised the Russian president.
He has also sharply criticized a U.S. Justice Department investigation into the alleged Russian meddling and whether his associates colluded with Moscow. Russia denies it interfered, despite substantial evidence, and Trump says there was no collusion.