WASHINGTON, April 12 – U.S. Secretary of State Anthony Blinken and NATO Secretary-General Jens Stoltenberg said Russia needed to immediately “cease its aggressive military buildup” along Ukraine’s borders, the State Department said in a statement Monday.

The two officials spoke ahead of Blinken’s upcoming trip to Brussels this week as Russia has been amassing its troops along the Ukrainian border in an apparent preparation for an attack.

Ukraine's government said on Monday that requests by President Volodymyr Zelenskyy to speak with his Russian counterpart Vladimir Putin about the escalating conflict in eastern Ukraine had been ignored. Moscow denied receiving any request from Kyiv for such talks, CBS News reported.

Tension between the neighbors has grown steadily for several weeks, with intensified skirmishes in eastern Ukraine. Putin has sent thousands of forces toward the Ukrainian border recently, raising concerns among politicians in the United States and European Union.

"The president's office, of course, made a request to speak with Vladimir Putin. We have not received an answer yet and we very much hope that this is not a refusal of dialogue," Ukrainian presidential spokeswoman Iuliia Mendel told Reuters on Monday.

She told Russia's Interfax news agency that the request for talks was sent on March 26, after four Ukrainian servicemen were killed by shelling in the country's east.

Kremlin spokesman Dmitry Peskov told reporters that he "hasn't seen any requests in the past several days."

Mendel said Russia had massed more than 40,000 troops on Ukraine's eastern border, and more than 40,000 in Crimea, the region that Putin unilaterally annexed away from Ukraine and declared Russian in 2014.

Mendel said Zelenskyy would travel to Paris for talks this week on Russia's actions and the escalating conflict in Ukraine's eastern Donbass region, Reuters reported.

German Defense Minister Annegret Kramp-Karrenbauer on Monday called on Moscow to declare its intentions in the region, saying that if Putin's government "has nothing to hide, it could easily explain why troops are being moved."

Manfred Weber, a prominent Member of the European Parliament from Germany, called Russia's troop buildup a test for the West, warning that if the situation continues to escalate, Moscow should face new sanctions.

"The answer needs to be clear and tough," he said.

In an interview with CNN given as he visited his troops on the front line, Zelenskyy said Ukraine, "needs more than words" of support from Washington and other European allies as it faces off with Russia.

The Kremlin has repeatedly said that Russia's military forces are free to move around within the country's territory as they see fit, and that the troop movements near the Ukrainian border — exercises, according to Moscow — pose no threat. (tl/rt/cbs/ez)