Sen. John McCain John Sidney McCainCOVID response shows a way forward on private gun sale checks Trump pulls into must-win Arizona trailing in polls Nonprofit 9/11 Day bashes Trump for airing political ads on Sept. 11 anniversary MORE (R-Ariz.) is calling on President Trump to send lethal aid to Ukraine after attacks this week were blamed on Russia-backed rebels.

“In the first of what will be many tests for your new administration, Russia and its proxy forces launched attacks against Ukrainian forces this week, killing at least seven Ukrainian soldiers and wounding dozens more,” McCain wrote in a letter to Trump released Thursday.

“That this surge of attacks began the day after he talked with you by phone is a clear indication that [Russian President] Vladimir Putin is moving quickly to test you as commander-in-chief. America’s response will have lasting consequences.”

Trump has expressed hope at improving relations with Russia and on Saturday spoke with Putin for the first time since Inauguration Day in what was described by the White House as a “positive call” that “was a significant start to improving the relationship.”

ADVERTISEMENT

The call included discussion of “the main aspects of the Ukrainian crisis,” according to the Kremlin statement about the call, though the White House statement did not mention Ukraine.

On Sunday, violence flared in the Avdiivka-Yasynuvata area and was described by some as the worst escalation since the conflict in eastern Ukraine began in 2014. Russia has denied backing the separatists, but Western officials have said otherwise.

The Russian Foreign Ministry has blamed Ukrainian troops for the latest violence.

Under the annual defense policy bill, the U.S. president already has the authority to send lethal aid to Ukraine such as weapons and ammunition. Former President Barack Obama Barack Hussein ObamaBiden to hold call with Senate Democrats on Thursday: report Romney undecided on authorizing subpoenas for GOP Obama-era probes Billboards in four states and DC demand ICE 'free the families' MORE opted not to use the authority, instead sending non-lethal aid, such as economic assistance.

But McCain, a staunch Russia hawk, urged Trump to use the authority given to him by Congress.

“Vladimir Putin’s violent campaign to destabilize and dismember the sovereign nation of Ukraine will not stop unless and until he meets a strong and determined response,” wrote McCain, chairman of the Senate Armed Services Committee.

McCain also reiterated his call for Trump to maintain sanctions on Russia and impose new ones for Russia’s interference in the U.S. election.

Failing to provide more help to Ukraine, McCain said, risks the country’s sovereignty and American credibility.

“Ukrainians are not asking Americans to do their fighting,” McCain said. “Nearly 10,000 Ukrainians have died to protect their homeland and many more are serving and have sacrificed for the cause of a free and united Ukraine. But America does have a proud history of helping free people to defend themselves.”