Paris: France President Emmanuel Macron’s office on Monday said that Russian President Vladimir Putin and US President Joe Biden have agreed to participate in a summit. US President Joe Biden accepted to participate in the summit only if Moscow does not invade Ukraine, in a frantic new round of diplomacy to avert an all-out war.

Both Presidents have accepted the proposal of French President Emmanuel Macron, said his office. Senior administration official sources said that timing to be determined and format to be determined so it’s all completely notional. Summit will be expanded to relevant stakeholders and that preparations would start between Russia and the United States on Thursday, said the source.

The possible breakthrough came after Washington warned of an imminent invasion and Ukraine and Russia blamed each other for a spike in shellings on the front line separating Kyiv’s forces from Moscow-backed separatists. The bombardments have sent Ukrainians fleeing to cellars and other shelters, while some civilians have been evacuated.

US warned that it was still ready to impose swift and severe consequences should Russia invade, White House said in a statement. Russia appears to be continuing preparations for a full-scale assault on Ukraine very soon, said US press secretary Jen Psaki. Washington and other Western capitals say that Russia has amassed more than 150,000 troops on Ukraine’s borders and is ready to launch a full-scale assault.

        The announcement of the summit came moments after Macron held his second marathon call with Putin of the day. Satellite images from a US company also showed new Russian troop deployments along the border. Macron also spoke with Ukraine’s Volodymyr Zelensky, who called for an immediate ceasefire and the resumption of talks.