MOSCOW - Kremlin spokesman Dmitry Peskov Tuesday blamed the United States for “building up tension” over Ukraine, as Russia launched new military exercises in the west of the country involving short-range ballistic missile units.

Peskov said Russia was closely watching U.S. moves, including the Pentagon’s decision to put 8,500 troops on high alert Monday for possible deployment to Europe.

“We are observing these actions of the United States with profound concern,” Peskov said, speaking to journalists Tuesday.

Russia’s Western Military District announced the exercises Tuesday, releasing video of Iskander short-range ballistic missile crews entering field positions, the latest in a rapid-fire series of drills that Russia has run in recent weeks, increasing pressure on NATO and Ukraine.

The Russian Defense Ministry also announced the arrival of Pacific Fleet forces in Belarus on Tuesday, ahead of a major military exercise with that country next month, fueling Western alarm over a possible Russian invasion of Ukraine. Russian officials have denied that they have plans to attack.

Altogether, Russia has massed military equipment and more than 100,000 troops near Ukraine and continues to move troops into place.

The moves come amid a flurry of diplomatic efforts to find a way out of the crisis, but the United States and NATO have firmly ruled out Moscow’s core demand against further NATO expansion, raising fears that Russia could use the failure of diplomacy as a pretext for the “military-technical” response that President Vladimir Putin has threatened.

Russian officials blame “Western aggression” for the crisis, repeatedly warning that Moscow will accept nothing less than an end to NATO’s long-standing open-door policy for new member countries.

Peskov said that Russia was awaiting a written response “this week” from Washington and NATO to its security demands, including that Ukraine and other countries be barred from NATO membership, and that the alliance remove troops and equipment from Eastern Europe.

He added that Putin would speak to French President Emmanuel Macron before the end of the week, after French officials said Paris would present a de-escalation plan to the Russian leader and Ukrainian President Volodymyr Zelensky.

Paris is set to host talks between political advisers Wednesday in an effort to reinvigorate the stalled Normandy Format peace process, involving France, Germany, Russia and Ukraine, designed to settle the conflict in the two Russian-backed separatist regions of eastern Ukraine that has been running since 2014.

Meanwhile, President Joe Biden sought to show a united front with European allies Monday after cracks emerged in recent weeks over which sanctions against Russia should be on the table in case of an attack, and over the supply of defensive weapons to Ukraine. Germany and Sweden have ruled out supplying Kyiv with weapons.

Biden insisted there was “total unanimity” among European leaders on Monday’s video call. The leaders - including Macron, British Prime Minister Boris Johnson and top NATO and European Union officials - spoke of their “shared desire for a diplomatic resolution to the current tensions,” according to a White House readout of the call.

They also discussed preparations to impose “massive consequences and severe economic costs” on Russia, as well as moves to reinforce security on NATO’s eastern flank. The Western alliance said Monday it was moving more military equipment into Eastern Europe, sending additional ships and fighter jets, just as the Biden administration put the U.S. troops on heightened alert for potential deployment.

Macron said during the virtual meeting that de-escalating the situation would require “strong, credible warnings to Russia” and “constant coordination among European partners and allies.” Paris has a tradition of pushing for European diplomacy to be more independent of Washington. But Macron’s expressed desire to strengthen E.U. involvement in the crisis comes as some Baltic states push for greater U.S. involvement and support.

“The biggest deterrence to Russia is an American flag,” Estonian Prime Minister Kaja Kallas told the Financial Times of London newspaper in an interview published Monday. Tensions in the Baltics are intensifying in tandem with the Ukraine crisis, as Moscow has issued a demand for the removal of all NATO military infrastructure installed after 1997 in Eastern European countries that are now members of the alliance.

In Belarus, which borders Ukraine, a group of hackers calling itself “Cyber Partisans” said Monday they had infiltrated the railway network of the Kremlin-aligned state to “disrupt” the movement of Russian troops. The group, announcing its intrusion in posts on Twitter and Telegram, said it had encrypted the railroad’s “servers, databases and workstations to disrupt its operations” because it facilitates the passage of “occupying troops.”

Minsk said Russian troops continued to arrive in the country ahead of the training exercise next month. Video surfaced on social media Monday showing Russian military convoys and trains with military equipment moving across southern Russia and Belarus.

Cyber Partisans said it would return the network to “normal mode” if 50 political prisoners in need of medical care were released and Russian troops were barred from Belarus. As of Monday evening, parts of the Belarusian Railway website were down, showing an error message that “the site is temporarily unavailable, come back later.”

Meanwhile, Canadian officials said Monday that hackers had launched an attack on the country’s Foreign Ministry last week, around the time Ottawa’s cyberdefense agency was warning of Russian-backed threats. Canada is a NATO member, and Prime Minister Justin Trudeau has been vocal in his opposition to Russia’s massing of forces on the Ukrainian border.

The Treasury Board Secretariat, which is responsible for Canadian government operations, didn’t immediately respond to a request for comment on whether Russian actors were responsible.

“Critical services for Canadians through Global Affairs Canada are currently functioning. Some access to Internet and internet-based services are not currently available as part of the mitigation measures and work is underway to restore them,” the Treasury Board said in a statement.

Amid the escalating tensions, U.S. Senate Majority Leader Charles Schumer, D-N.Y., requested that the Biden administration brief members of the upper chamber on the Russia-Ukraine situation, a person familiar with the matter said. House Speaker Nancy Pelosi, D-Calif., has requested a similar bipartisan briefing.

Even as the administration seeks a diplomatic resolution to the Ukraine crisis, the United States and some Western allies have begun to take the kind of dramatic steps typically reserved for the eve of anticipated armed action.

Britain pulled some diplomats and their families out of Ukraine on Monday, a day after the United States ordered families of diplomats to leave Kyiv and authorized the departures of nonessential embassy staff.

In an interview with the ITV network, British leader Johnson said intelligence indicates Russia is planning a “lightning raid” on Kyiv, as he warned the Kremlin that an incursion would be “a disastrous step” that could lead to a lengthy conflict with casualties on both sides.

Pannett reported from Sydney. The Washington Post’s Bryan Pietsch in Seoul, Amanda Coletta in Toronto and Ashley Parker, Missy Ryan and Karoun Demirjian in Washington contributed to this report.