US Secretary of State John Kerry will meet Russian President Vladimir Putin in Sochi on Tuesday for talks on Ukraine, Syria and Iran.
Mr Kerry's trip to Russia - his first since 2013 - is aimed at maintaining "direct lines of communication" with the Kremlin and to "ensure US views are clearly conveyed", the US State Department said.
The visit comes amid a period of heightened tension between the US and Russia over the latter's actions in the Ukraine conflict.
A diplomatic source was quoted by Russian media as saying that Kerry's visit "is very symbolic".
The US Secretary of State John Kerry has cancelled plans to return to the USA to continue Iran nuclear talks in Switzerland amid signs of troubled negotiations.
He was due to return to the USA to attend an event honoring his late colleague Edward Kennedy, the dedication of the Kennedy Institute in Boston with the late senator's family.
But the State department said that "given the ongoing nuclear negotiations in Switzerland, the secretary regrets he will not be able to share this special time with them in person."
His decision to stay comes as the talks appear to have hit obstacles ahead of a March 31 target for the outline of a final deal to be negotiated by the end of June.
US Secretary of State John Kerry has said America will "in the end" have to negotiate with Syria's President Assad, according to CBS News.
Kerry said the US is willing to negotiate within the context of the Geneva process, which calls for negotiated political transition in Syria.
America and "other countries" are exploring ways to reignite the diplomatic process in Syria, he added.
But Kerry admitted that getting Assad to negotiate may require increased pressure on him.
Secretary of State John Kerry said the US had no intelligence on who was behind the shooting of Russian opposition politician Boris Nemtsov.
"The bottom line is we hope there will be a thorough, transparent, real investigation, not just of who actually fired the shots, but who, if anyone, may have ordered or instructed this or been behind this," he told ABC News' This Week.
US Secretary of State John Kerry has said that he and his European counterparts are agreed that the conflict in eastern Ukraine "will not end through military force".
He emphasised that there was "no split" between US and European policy towards Ukraine.
"We will stand together in support of Ukraine and in defence of the common understanding that international borders ... cannot be changed by force in Europe or anywhere else." Mr Kerry added.
John Kerry says that the largest threat to Ukraine is Russian aggression but that the west is not seeking conflict with Russia.
The Secretary of State says the US is seeking a diplomatic solution to the conflict in Ukraine but is not prepared to "close our eyes" to Russian tanks and fighters crossing the border.
Speaking after talks in Kiev with Ukrainian President Petro Poroshenko, Kerry demanded an immediate commitment by Moscow to a ceasefire in eastern Ukraine that was backed up by actions on the ground.
Russia has consistently rejected accusations from Kiev and the West that it supports a pro-Russian rebellion in eastern Ukraine with troops and heavy weaponry.
The US has pledged $16.4 million in humanitarian aid to help civilians in eastern Ukraine.
Secretary of State John Kerry arrived in Kiev this morning for talks with the embattled Ukrainian leadership.
US Secretary of State John Kerry has written on Twitter:
US Secretary of State John Kerry has said that the insurgency by Islamic State militants in northern Iraq and Syria demands a "much fuller response" than just airstrikes.
Writing in the New York Times, he said:
Airstrikes alone won’t defeat this enemy. A much fuller response is demanded from the world. We need to support Iraqi forces and the moderate Syrian opposition, who are facing ISIS on the front lines ... In this battle, there is a role for almost every country. Some will provide military assistance, direct and indirect. Some will provide desperately needed humanitarian assistance for the millions who have been displaced and victimized across the region. Others will help restore not just shattered economies but broken trust among neighbors.
US secretary of state John Kerry warned today that the violent acts carried out by Islamist militants in Iraq "show all the warning signs of genocide"
"With the potential of further executions taking place," he said, "and because people are a minority huddled for safety on a mountain top, the United States has made its decision that it must save these lives.
"The world needs to join us in the condemnation of these actions," Mr Kerry added, speaking in the Afghan capital of Kabul.