Ukraine’s defence minister said Russia’s military buildup along its borders could bring more troops into the region and potentially extend to using Crimea, annexed from Ukraine seven years ago, for storing nuclear weapons.

Andriy Taran was addressing a meeting of the European Parliament’s Defence Subcommittee as both Russia and Ukraine staged military drills and NATO ministers held talks devoted largely to the Russian mobilisation.

Those talks came a day after U.S. President Joe Biden urged Kremlin leader Vladimir Putin in a telephone conversation to “de-escalate tensions” quickly at different points along the Ukrainian border.

Ukrainian officials say 40,000 troops have been moved into a place adjacent to Donbass, where separatists aligned with Moscow set up two “people’s republics” seven years ago, with a further 40,000 deployed in Crimea. Russia says the deployment is an active exercise undertaken in response to aggressive actions by NATO and will continue for a further two weeks.

More troops coming

Taran told members of the European Parliament those numbers were likely to swell to 110,000 in the coming days. And Russia, he said, could well be preparing the ground to deploy nuclear weapons.

“Crimea’s infrastructure is being readied for potentially storing nuclear weapons,” Taran said.

“The very presence of nuclear munitions may spark a whole array of complex political, legal and moral problems.”

The minister provided no proof to underpin his assertion. Ukraine initially took control of nuclear missiles from the Soviet-era arsenal, but voluntarily gave them up in the 1990s at the urging of Western nations in exchange for guarantees that its borders would be inviolable, guarantees it says were shattered by Russia’s seizure of Crimea.

Taran also said Russia could be considering intervention in southern Ukraine from Crimea to secure control over a canal previously used to supply the peninsula with water.

In Kyiv, the head of the Ukrainian defence ministry’s intelligence directorate, Kyrylo Budanov, said several scenarios were being considered – an attack to secure the canal, a more direct military advance from Crimea or provocative moves against targets in Donbass that would then be exploited to accuse Ukraine of violating an intermittent ceasefire first put in place last year

He said the entire deployment of Russia’s additional forces, which he also estimated at 110,000, would be in place by April 20.

Too early for summit, Russia says

During the telephone call between the White House and Kremlin, Biden proposed a summit meeting in a third country.

The Kremlin on Wednesday said it was too early to consider a summit and suggested prospects for such a meeting depended on Washington’s actions – a likely reference to the possible imposition of new Western sanctions.

The head of Russia’s Security Council, Nikolai Patrushev, was in Crimea on Wednesday and warned of possible Ukrainian attacks on infrastructure in the region stemming from “the destructive activity of the United States and the NATO bloc controlled by it,” Itar-Tass news agency reported.

Russian officials have denounced the dispatch this week of two U.S. warships to the Black Sea. The Russian drills, with firing on surface and air targets, got underway a day after NATO Secretary-General Jens Stoltenberg met Ukrainian Minister Dmytro Kuleba and told Moscow to halt the buildup in the region.

The Ukrainian exercises focused on a mock operation to repel a tank and infantry attack near the border of annexed Crimea.

Kuleba’s talks in Brussels focused on Kyiv’s case for NATO to consider extending membership to Ukraine – a notion viewed as anathema in Moscow.

The prospects of NATO seriously considering Ukraine’s bid for membership are uncertain to say the least.  But U.S. Secretary of State Antony Blinken said NATO would “address Russia’s aggressive actions in and around Ukraine”.

Ukrainian President Volodymyr Zelensky, who won office with pledges of stopping the fighting by clinching a deal with Moscow, has now adopted a much tougher stand. He said earlier this month that he saw Ukrainian membership of the Atlantic Alliance as the only way to stop the conflict in Donbass, in which sone14,000 have died.

Zelensky has embarked on a series of diplomatic forays to advance Ukraine’s case in its standoff with Moscow.

He plans to meet French President Emmanuel Macron in Paris on Friday.