U.S. says Biden agrees 'in principle' to summit with Putin if Russia doesn't invade Ukraine

The U.S. and Russian presidents have tentatively agreed to meet in a last-ditch diplomatic effort to stave off Moscow's invasion of Ukraine as heavy shelling continued Monday in a conflict in eastern Ukraine that is feared will spark the Russian offensive.

French President Emmanuel Macron sought to broker a possible meeting between U.S. President Joe Biden and Russian President Vladimir Putin in a series of phone calls that dragged into the night.

Macron's office said both leaders had "accepted the principle of such a summit," to be followed by a broader summit meeting also involving other "relevant stakeholders to discuss security and strategic stability in Europe." It added that the meetings "can only be held on the condition that Russia does not invade Ukraine."

White House press secretary Jen Psaki, said the Biden administration has been clear that "we are committed to pursuing diplomacy until the moment an invasion begins." She noted that "currently, Russia appears to be continuing preparations for a full-scale assault on Ukraine very soon."

Macron's office said that U.S. Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov are set to lay the groundwork for the summit when they meet on Thursday.

News that Putin and Biden could meet followed a flurry of calls by Macron to the two leaders, as well as to British Prime Minister Boris Johnson and Ukrainian President Volodymyr Zelensky.

Kremlin spokesperson Dmitry Peskov said Monday that Putin and Biden could meet if they consider it necessary, but emphasized that "it's premature to talk about specific plans for a summit."

"The meeting is possible if the leaders consider it feasible," he said in a conference call with reporters.

Blinken intentionally raised the prospect of a Biden-Putin summit in interviews with U.S. television networks on Sunday, in a bid to keep diplomacy alive, a senior U.S. official said. The official spoke on condition of anonymity to discuss U.S. reasoning.

Blinken said that Biden was "prepared to meet President Putin at any time in any format if that can help prevent a war" and the U.S. official said Macron had then conveyed the offer of talks to Putin — conditioned on Russia not invading — in his phone calls with the Russian leader.

The prospective meeting offers new hope of averting a Russian invasion that U.S. officials said could begin any moment with an estimated 150,000 Russian troops amassed near Ukraine.

Adding to fears of an imminent attack, Russia and its ally and neighbour Belarus announced Sunday that they were extending massive war games on Belarusian territory that offers a convenient bridgehead for an attack on the Ukrainian capital, Kyiv, located just 75 kilometres south of the border with Belarus.

Since last Thursday, shelling has spiked along the tense line of contact between Ukrainian forces and Russian-backed separatists in Ukraine's eastern industrial heartland, Donbas, where over 14,000 people have been killed since conflict erupted in 2014 shortly after Moscow's annexation of Ukraine's Crimean Peninsula.

Ukraine and the separatists have traded blame for innumerable ceasefire violations with hundreds of explosions recorded daily.