Germany has accused Russia of seeking provocation with its troop buildup in the occupied Crimean Peninsula and along the border with Ukraine, while rejecting Moscow's claim that it was responding to threats from NATO.
"My impression is that the Russian side is trying everything to provoke a reaction," German Defense Minister Annegret Kramp-Karrenbauer told public broadcaster ARD television on April 14.
"Together with Ukraine, we won't be drawn into this game," she said, adding it was clear that Russia "is just waiting for a move, so to speak, from NATO, to have a pretext to continue its actions."
Recent photographs, video, and other data suggest major movements of Russian armed units toward or near Ukraine's borders and into Crimea, seized by Moscow in 2014, fueling concerns that Russia is preparing to send forces into Ukraine.
Ukraine and the West also blame Moscow-backed separatists holding parts of the country's eastern regions of Donetsk and Luhansk for a recent spike in hostilities, while Moscow has pointed the finger at Kyiv.
Kramp-Karrenbauer also cast doubt on Moscow's claim that the buildup is in response to "threats" from the transatlantic alliance.
"If it is a maneuver, like the Russian side says, there are international procedures through which one can create transparency and trust," she said.
Russia annexed Ukraine's Crimean Peninsula in March 2014, sending in troops and staging a referendum denounced as illegitimate by at least 100 countries after Moscow-friendly Ukrainian President Viktor Yanukovych was ousted amid a wave of public protests.
Moscow also backs separatists in a war against Ukrainian government forces that has killed more than 13,000 people in eastern Ukraine since April 2014.
With tensions rising, U.S. President Joe Biden on April 13 urged his Russian counterpart, Vladimir Putin, to take measures to de-escalate the situation with Kyiv and proposed a summit between the two leaders in a third country.
In a phone call with Putin, Biden "voiced our concerns over the sudden Russian military buildup" while reaffirming "his goal of building a stable and predictable relationship with Russia consistent with U.S. interests, and proposed a summit meeting in a third country in the coming months to discuss the full range of issues facing the United States and Russia," a White House statement said.
Putin's spokesman, Dmitry Peskov, said on April 14 that the Kremlin will consider Biden's proposal.
"It is early to talk about this meeting in terms of specifics. This is a new proposal and it will be studied. There will be an analysis," he told reporters.
Such a summit would be the first between Putin and Biden, who took office vowing a tougher stance toward Moscow than the one taken by his predecessor, Donald Trump.
Some analysts have suggested that Russia’s recent actions may be meant to test the new U.S. administration and its commitment to Ukraine.
The Kremlin has rejected Western calls to pull back its troops from the border region, denying they are a threat and adding that military movements within Russia are an internal sovereign issue.
It has also warned that Moscow "will not remain indifferent" to the fate of Russian speakers who live in Ukraine’s east.
Citing a Russian Foreign Ministry source, the RIA Novosti news agency reported that Putin's foreign-policy adviser, Yury Ushakov, had told the U.S. ambassador in Moscow on April 13 that Moscow would act decisively if the United States undertook any new "unfriendly steps," such as imposing sanctions.
Speaking to the Vesti FM radio station on April 14, Russian Foreign Ministry spokeswoman Maria Zakharova accused NATO of "playing games" with Kyiv, inciting politicians there to maintain tensions in eastern Ukraine, according to TASS.
The previous day, Russian Defense Minister Sergei Shoigu claimed that Moscow has deployed troops to its western borders for "combat training exercises" in response to NATO "military activities that threaten Russia."
But it was not clear to which activities Shoigu was referring, as the Western security alliance has denied making any military moves in the region.
Shoigu didn't elaborate, but he could have been referencing the DEFENDER-Europe 21 military exercises taking place in Europe and Africa, which began in March and involve almost 30,000 troops from 26 countries.
Nearly 30 Ukrainian soldiers have been reported killed since the start of the year, compared with 50 in all of 2020. Separatists have said more than 20 of their fighters had been killed so far in 2021.
The exercises, which will run into June, are taking place in various countries, including Estonia -- which shares a border with Russia -- Bulgaria and Romania.
According to Ukrainian President Volodomyr Zelenskiy's office, Russia has massed more than 40,000 troops both on Ukraine's eastern border and in the occupied Crimean Peninsula.
Kyiv has so far reacted in a "sober" manner, the German defense minister said in the ARD interview, stressing that NATO allies were "committed to Ukraine, that is very clear."
On April 13, Ukrainian Foreign Minister Dmytro Kuleba held talks in Brussels with NATO chief Jens Stoltenberg and U.S. Secretary of State Antony Blinken, who accused Russia of taking "very provocative" actions.
Blinken also affirmed the United States' "unwavering support for Ukraine’s sovereignty and territorial integrity in the face of Russia’s ongoing aggression."
At a news conference, Stoltenberg called on Moscow to end "the largest massing of Russian troops since the illegal annexation of Crimea in 2014," saying the movements were "unjustified, unexplained, and deeply concerning."
Meanwhile, Ukraine's military said one of its soldiers was killed and three wounded on April 13 when separatists fired 82-millimeter mortar rounds toward Ukrainian positions, as well as grenade launchers, heavy machine guns, and automatic rifles.
Nearly 30 Ukrainian soldiers have been reported killed since the start of the year, compared with 50 in all of 2020, when fighting in the conflict subsided as a new cease-fire deal came into force in July.
Separatists in Donetsk and Luhansk regions have said more than 20 of their fighters have been killed so far in 2021.
Highlighting the growing tensions between Kyiv and Moscow, Ukrainian Defense Minister Andriy Taran said on April 14 that Russia is preparing Crimea for potentially storing nuclear weapons and warned that Moscow could attack Ukraine to ensure water supplies for the annexed peninsula.
Taran, who made the statement to the European Parliament's defense sub-committee in Brussels, did not immediately provide evidence for his assertions.
Meanwhile, the Ukrainian military said it had deployed tanks and artillery near the administrative border of Crimea on April 14 to practice repelling a force of tanks and infantry trying to break through the country’s defenses.
The drills came as the Russian Navy began exercises in the Black Sea ahead of the expected arrival of two U.S. warships in the area this week, Russian news agencies reported.
The drills will involve surface vessels from Russia's Black Sea Fleet, which is based in Crimea, along with helicopters and planes, and will rehearse firing at surface and air targets, according to Interfax