WASHINGTON: US President Joe Biden urged his Russian counterpart Vladimir Putin to ease mounting tensions with neighboring Ukraine Tuesday, joining a pushback against a build-up of troops along their border that has alarmed NATO allies.

As a new report from American intelligence said Russia was not seeking direct conflict with the United States, Biden in a telephone conversation with Putin proposed a summit between the two leaders at a neutral venue in the coming months.

The Russian buildup at the Ukrainian border has caused growing concern in the West in recent days, with the United States saying that troop levels are at their highest since 2014, when war first broke out with Moscow-backed separatists.

Biden "voiced our concerns over the sudden Russian military build-up in occupied Crimea and on Ukraine's borders, and called on Russia to de-escalate tensions," the White House said after the phone call. White House Press Secretary Jen Psaki said Biden was "not looking for an establishment of trust as much as a predictability and stability" in relations with Russia.

The Kremlin said it would "continue dialogue" without accepting the offer for a first summit with Biden, who came to office vowing a tougher line on Russia including over its alleged interference in US elections and harsh treatment of ailing opposition leader Alexei Navalny.

Putin similarly held a summit in Finland in 2018 with then-US president Donald Trump, who caused a furor at home by appearing to accept the Russian leader's denials of election meddling.

The Biden-Putin call came as Ukrainian Foreign Minister Dmytro Kuleba met in Brussels with top officials of NATO nations including Secretary of State Antony Blinken and the transatlantic alliance's chief, Jens Stoltenberg.

"Russia's considerable military build-up is unjustified, unexplained and deeply concerning -- Russia must end this military build-up in and around Ukraine, stop its provocations and de-escalate immediately," Stoltenberg said at his meeting with Kuleba.

The US secretary of state also met with EU foreign policy chief Josep Borrell, both of whom expressed deep concern over Russian troop movements, according to a European statement.

And in a clear sign that Washington is looking to bolster its backing for European allies, Defense Secretary Lloyd Austin announced the United States was sending some 500 new personnel to Germany.