"The president voiced our concerns over the sudden Russian military buildup in occupied Crimea and on Ukraine's borders, and called on Russia to de-escalate tensions", the statement read. There is growing concern in the West about a surge of cease-fire violations in eastern Ukraine, where Russia-backed separatists and Ukrainian forces have been locked in a conflict since Moscow's 2014 annexation of Ukraine's Crimean Peninsula.
Earlier, the White House readout of Tuesday's telephone conversation between Putin and Biden said that the United States president had "voiced" Washington's "concerns over the sudden Russian military buildup in occupied Crimea and on Ukraine's borders, and called on Russia to de-escalate tensions".
It also said that Biden proposed a summit "in the near future" but did not say whether the idea had been accepted.
U.S. Secretary of State Antony Blinken, in Brussels for talks on Tuesday with North Atlantic Treaty Organisation leaders and Ukraine's foreign minister, echoed Biden, saying U.S. stood firmly behind Ukraine.
Defence Minister Sergei Shoigu said the manoeuvres in western Russian Federation that have anxious neighbouring Ukraine and brought warnings from North Atlantic Treaty Organisation would last for another two weeks.
In a new report released Tuesday, the director of USA national intelligence said that Russian Federation would "continue destabilization efforts against Ukraine" while concluding that "does not want a direct conflict" with the United States.
Ryabkov's remarks suggest that the diplomatic niceties which the former Cold War enemies have generally sought to observe in recent decades is fraying, and that Russian Federation would robustly push back against what it regards as unacceptable USA interference in its sphere of influence.
Amid the recent tensions, the United States notified Turkey that two US warships would sail to the Black Sea on April 14 and April 15 and stay there until May 4 and May 5.
"They are testing our strength and playing on our nerves", Ryabkov said in remarks carried by Russian news agencies.
"Russia's considerable military build-up is unjustified, unexplained and deeply concerning - Russian Federation must end this military build-up in and around Ukraine, stop its provocations and de-escalate immediately", Stoltenberg said at his meeting with Kuleba. He called Russia's actions "very provocative".
Russian Federation in recent weeks has stepped up troop movements near its border with Ukraine.
"Russia must end this military build-up in and around Ukraine, stop its provocations and de-escalate immediately", Stoltenberg said at a news conference with Kuleba. "NATO stands with Ukraine", he said. It has regularly accused North Atlantic Treaty Organisation of destabilising Europe with its troop reinforcements in the Baltics and Poland since the annexation of Crimea. North Atlantic Treaty Organisation is holding a special meeting Tuesday on Ukraine.
In an interview last month, Biden labeled Putin a "killer," prompting an angry reaction from Moscow, which recalled its ambassador from Washington.
Tensions remain high in the Donbass border region which has been dogged by conflict between Ukraine troops and separatists since 2014.
"In total, 40,000 troops and 15,000 weapons and pieces of military equipment are concentrated near our territory, including strategic aircraft", Shoigu said.
Kuleba said Kyiv wanted a diplomatic solution.
Kuleba appealed for further economic sanctions against Moscow and more military help to Kyiv. We don't believe in such terminology: "price, retribution and so on", he said. We support Ukraine's posture of restraint.
During the conversation, they discussed various issues, including the Ukraine crisis.
"In this struggle, the support of the United States is absolutely crucial and deeply appreciated", Kuleba said.