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 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 Sergey Lavrov are set to lay the groundwork for the summit when they meet Thursday.

It followed a flurry of calls by Macron to Putin, Biden and also British Prime Minister Boris Johnson and Ukrainian President Volodymyr Zelenskyy.

Kremlin spokesman 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.

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 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 kilometers (less than 50 miles) south of the border with Belarus.

Starting Thursday, shelling also spiked along the tense line of contact between Ukrainian forces and Russian-backed separatist rebels 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 rebels have traded blame for massive cease-fire violations with hundreds of explosions recorded daily.

On Friday, separatist officials announced the evacuation of civilians and military mobilization in the face of what they described as an imminent Ukrainian offensive on the rebel regions. Ukrainian officials have strongly denied any plans to launch such an attack and described the evacuation order as part of Russian provocations intended to set the stage for an invasion.

The separatist authorities said Monday that at least four civilians were killed by Ukrainian shelling over the past 24 hours and several others were injured. Ukraine’s military said two Ukrainian soldiers were killed over the weekend, and another serviceman was wounded Monday.

Ukrainian military spokesman Pavlo Kovalchyuk said the Ukrainian positions were shelled 80 times Sunday and eight times early Monday, noting that the separatists were “cynically firing from residential areas using civilians as shields.” He insisted that Ukrainian forces weren’t returning fire.

In the village of Novognativka on the government-controlled side, 60-year-old Ekaterina Evseeva, said the shelling was worse than at the height of fighting early in the conflict.

“It’s worse than 2014,” she said, her voice trembling. “We are on the edge of nervous breakdowns. And there is nowhere to run.”

Evseeva said that residents were hunkering down in basements amid the renewed fighting: “Yesterday I saw my neighbor with her 2-month-old as she was running to the basement. It shouldn’t be like this.”

Amid the heightened invasion fears, the Kremlin reacted angrily to a New York Times report that the U.S. administration has sent a letter to the United Nations human rights chief claiming that Moscow has compiled a list of Ukrainians to be killed or sent to detention camps after the invasion. Peskov, the Kremlin spokesman, said the claim was a lie and no such list exists.

Moscow denies any plans to invade Ukraine, but wants Western guarantees that NATO won’t allow Ukraine and other former Soviet countries to join as members. It also urges the alliance to halt weapons deployments to Ukraine and roll back its forces from Eastern Europe — demands flatly rejected by the West.

Russian officials have shrugged off Western calls to deescalate by pulling back troops, arguing that Moscow is free to deploy troops and conduct drills wherever it likes on its territory. Last week, Western officials dismissed Russian statements about some of the troops returning to their bases, saying that Moscow was actually beefing up its forces around Ukraine.

Despite Biden’s assertion last week that Putin has made the decision to roll Russian forces into Ukraine, Ukrainian officials sought to project calm, saying that they aren’t seeing invasion as imminent.

Defense Minister Oleksii Reznikov said Monday that Russia has amassed 147,000 troops around Ukraine, including 9,000 in Belarus, arguing that the number is clearly insufficient for an offensive on the Ukrainian capital from the north.

“The talk about an attack on Kyiv from the Belarusian side sounds ridiculous,” he said, charging that Russia is using the troops there as a scare.

Russia upped the ante Saturday with sweeping nuclear drills that included multiple practice launches of intercontinental ballistic missiles and cruise missiles that Putin personally oversaw.

The European Union’s top diplomat, foreign policy chief Josep Borrell, welcomed the prospect of a Biden-Putin summit but said that should diplomacy fail the 27-nation bloc has finalized its package of sanctions for use if Putin orders an invasion.

“The work is done. We are ready,” said Borrell, who is chairing a meeting of EU foreign ministers and was tasked with drawing up a list of people in Russia to be hit with asset freezes and travel bans. He provided no details about who might be targeted.

German Foreign Minister Annalena Baerbock welcomed Macron’s summit initiative and warned Russia against any false flag action to provoke hostilities. “I appeal urgently to the Russian government, to the Russian president: Don’t play with human lives,” she said as she arrived at the EU top diplomats’ meeting.

(AP)