The Biden administration, facing what could be its first serious test with Russia, is warning Moscow against any aggressive use of the military force that it’s assembling along Ukraine’s eastern border for a supposed exercise.

“We are quite concerned by recent escalation by Russia” along the border, “including violations of the July 2020 cease-fire” in a March 26 incident that killed four Ukrainian soldiers and wounded two, a senior administration official told me Wednesday night.

Russia has announced military exercises in the region, and Russian social media posts show tanks, howitzers and other heavy military equipment moving into the area. “Maybe these are exercises, maybe more,” the official said during the interview.

“We are signaling American awareness, resolve and concern,” he continued. The National Security Council’s deputies committee met Tuesday and Wednesday to review the situation, he said, and national security adviser Jake Sullivan has called his Ukrainian, German and British counterparts. A meeting of NATO’s North Atlantic Council is scheduled for Thursday.

Russia has accused Ukraine of provoking the confrontation. “We express concern . . . that one way or another the Ukrainian side could take provocative actions that would lead to war. We really don’t want to see that,” Kremlin spokesman Dmitry Peskov said Wednesday.

Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, called his Russian and Ukrainian counterparts, Gen. Valery Gerasimov and Lt. Gen. Ruslan Khomchak, on Wednesday. Milley’s spokesman wouldn’t discuss the call. So far, Pentagon officials see evidence of a training operation, rather than preparations for an invasion, but they are monitoring the situation closely.

“We are not looking to reset our relations with Russia nor to escalate. Our goal is to impose costs for actions we consider unacceptable, while seeking stability, predictability, turning down the temperature,” the senior Biden administration official said, adding: “If they’re inclined to turn the temperature up, we’re ready for that.” U.S. options include expedited assistance to Ukraine and sanctions.

The Ukraine border tension comes as Russian President Vladimir Putin faces his most substantial domestic criticism in several years. Much of it centers on opposition politician Alexei Navalny, whose arrest in January sparked protests in at least 109 cities across Russia. Navalny had bravely returned to Moscow after being treated abroad following an assassination attempt last August. Navalny began a hunger strike Wednesday to protest his treatment in prison.

Putin probably had hoped that jailing Navalny would make that political problem disappear, but it continues. A petition calling for further demonstrations has been signed by 360,000 Navalny supporters, and organizers hope to gather 500,000 signatures before taking to the streets again.

“Elements of this are reminiscent of the run-up to Russia’s previous intervention in Ukraine” in 2014, when Putin was facing domestic criticism, the senior official said. In addition to the Navalny controversy, Russians have blamed Putin for corruption and a sluggish response to the coronavirus pandemic.

Sanctions against the Russian petroleum sector are having an effect, blocking access to needed Western technology, an industry source tells me. Russia attempted to increase production in recent months in aging fields, for example, but output continues to decline because they lack modern equipment.

The Biden administration’s stern messaging about Russia this week is the latest example of how the White House and State Department are trying to bolster U.S. foreign policy after the disruption and disorganization of the Trump years. The centerpiece of that strategy has been rebuilding alliances — with NATO countries when it comes to confronting Russia, and with key Asian allies such as Japan, India and Australia (known collectively, with the United States, as the Quad) in competing with China.

Biden has tried to signal a firmer stance toward Russia since taking office. The day after his inauguration, he ordered a review of Russia’s role in the aggressive SolarWinds hack that affected thousands of companies and government agencies. On Feb. 4, following Navalny’s arrest, Sullivan warned: “Unlike the previous administration, we will be taking steps to hold Russia accountable for the range of malign activities that it has undertaken.”

There is often jockeying and positioning during the initial months of new U.S. administrations, as potential adversaries probe each other’s limits. China’s top diplomat delivered a public tongue-lashing to Secretary of State Antony Blinken at their first meeting, in Anchorage last month, for example. Diplomacy, in other words, is a contact sport.

What makes the Ukraine situation different is that it potentially involves force. Russia has augmented its troops, at least temporarily, near the border of a country to which the United States provides military assistance. Perhaps the best thing about this week’s signaling is that it reduces the likelihood that either side will miscalculate its actions.

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