The Kremlin said Monday that there were no concrete plans for a meeting between Russian President Vladimir Putin and his US counterpart Joe Biden over Ukraine, after French President Emmanuel Macron said the two leaders had agreed in principle to meet.

A summit could offer a way out of Europe’s worst military crisis in decades, and European financial markets rose on the prospect of a diplomatic solution. However, by 1200 GMT, they were in the red, with Russian stocks falling 7-8%.

Both Washington and Moscow downplayed the possibility of a breakthrough, and satellite imagery appeared to show Russian deployments closer to Ukraine’s border than previously.

Western countries accuse Russia of plotting an invasion of a neighbor it ruled for centuries until the Soviet Union imploded in 1991. Moscow has denied any plans for an attack, but has demanded broad security guarantees, including a guarantee that Ukraine will never join NATO.

Moscow’s close ally Belarus announced on Sunday that Russia would extend military exercises there, further fraying nerves.

Russia has tens of thousands of soldiers in Belarus, part of what Washington claims is a regional force of 169,000-190,000 troops, including pro-Russian rebels in eastern Ukraine.

Following talks with NATO Secretary-General Jens Stoltenberg in Brussels, British Foreign Minister Liz Truss stated that Western countries were preparing for a “worst-case scenario.” The airlines Lufthansa, KLM and Air France all canceled flights to Kyiv.

However, the European Union rejected Kyiv’s request to impose sanctions now in order to prevent a war from breaking out.

Dmitry Peskov, a Kremlin spokesperson, said a call or meeting between Putin and Biden could take place at any time, but there were no concrete plans for a summit as of yet. Tensions were rising, he said, but a meeting of foreign ministers was possible this week.

The substance of the plan will be worked out by US Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov during a meeting scheduled for Thursday, according to Macron’s office and the White House.

An adviser to French President Emmanuel Macron told Reuters that the summit proposal had been sent to Putin at Biden’s request.

Ukraine stated that any decisions aimed at resolving the crisis must include it, and that it had seen online warnings that hackers were planning cyberattacks on government agencies, banks, and the military.

Western countries claim that the sanctions they are planning will target Russian companies and individuals. According to people familiar with the situation, they could include prohibiting US financial institutions from processing transactions for Russian banks.

Putin has long been irritated by the rise of pro-Western politicians promising to advance democracy and combat corruption in Ukraine. When pro-Western protests forced a pro-Russian president to flee Kyiv in 2014, Russia retaliated by seizing Crimea from Ukraine and supporting rebels who took control of parts of the east bordering Russia.

Maxar, a satellite imagery company based in the United States, reported new Russian unit deployments in forests, farms, and industrial areas as close to the Ukrainian border as 15 kilometers (9 miles).

Since Thursday, sporadic shelling across the line separating government forces and pro-Russian insurgents has increased, with both sides trading blame.

Separatists have been busing civilians out, accusing Kiev of plotting an attack. Ukraine and the West see the insurgents as Russian proxies who are escalating in order to provide Moscow with justification to invade.

According to Russia’s FSB intelligence service, a shell fired from Ukrainian territory struck a Russian border guard post in the city of Rostov, but no one was injured. According to Russia’s RIA news agency, the rebels said two civilians were killed in shelling by Ukrainian government forces. According to Russian media, 61,000 evacuees from east Ukraine have crossed into Russia.

Kyiv denies firing on civilians or straying across the border. At a time when Russia has massed troops on the border, Washington says accusations that Kyiv would deliberately escalate the conflict are absurd.