SIMI VALLEY, Calif. ― When U.S. President Joe Biden speaks with Vladimir Putin Tuesday, Biden should emphasize sanctions and not American military might, the chairman of the House Armed Services Committee said Saturday.

“You’re not going to deter him by trying to flex your muscles and convince him that we’re going to confront them militarily and defeat them in Eastern Europe,” Rep. Adam Smith, D-Wash., said in an interview at the annual Reagan National Defense Forum.

“You’re going to flex your muscles by showing [Putin] that we have a strong set of allies who are prepared to make them pay economically and enormously,” Smith said.

The comments came as Biden and Putin are set to speak on a video call, the Kremlin said. Tensions between their two counties have escalated over a Russian troop buildup on the Ukrainian border. The troops are seen as a sign of a potential invasion.

Biden will press U.S. concerns about Russian military activities on the border and “reaffirm the United States’ support for the sovereignty and territorial integrity of Ukraine,” White House press secretary Jen Psaki said Saturday, confirming the planned call after first word came from Moscow.

Russia is more adamant than ever that the U.S. guarantees that Ukraine will not be admitted to the NATO military alliance. But NATO’s secretary-general, Jens Stoltenberg, said this past week that Russia has no say in expansion plans by other countries or the alliance. Several former U.S. and NATO diplomats say any such Russian demand to Biden would be a nonstarter.

The Kremlin said Friday that Putin, during his call with Biden, would seek binding guarantees precluding NATO’s expansion to Ukraine. Biden tried to head off the demand in comments to reporters Friday before leaving for a weekend stay at Camp David.

“I don’t accept anyone’s red line,” Biden said.

U.S. intelligence officials, meanwhile, have determined that Russia has massed about 70,000 troops near its border with Ukraine and has begun planning for a possible invasion as soon as early next year, according to a Biden administration official who was not authorized to discuss that finding publicly and spoke on the condition of anonymity.

The risks for Putin of going through with such an invasion would be enormous.

U.S. officials and former American diplomats say while the Russian president is clearly laying the groundwork for a possible invasion, Ukraine’s military is better armed and prepared today than in the past, and that sanctions threatened by the West would do serious damage to the Russian economy.

Smith argued that the threats of U.S. military aid to Ukraine and sanctions would prove effective deterrents. But threatening military action could provoke or create a pretext for Putin, who could decide to act first before western troops are deployed.

To boot, Smith argued the American people are not willing to go to war with Russia: “Putin knows that not only am I not, the American people aren’t.”

Some Republicans have voiced skepticism over Biden’s approach to the crisis.

The House Armed Services Committee’s ranking member, Rep. Mike Rogers, R-Ala., needled Biden in a pair of statements, one demanding Ukraine get more U.S. arms and another demanding it get a long-delayed path into NATO.

“There is an old Leninist adage that Putin lives by. ‘Probe with bayonets; if you encounter mush, proceed; if you encounter steel, stop.’ The time to accelerate the flow of steel in the form of heavy weapons to Ukraine was weeks ago,” Rogers said. “Every day that you hesitate in doing so only invites further aggression. The world is watching, Mr. President.”

Iowa Republican Sen. Joni Ernst said she wants Biden to tell Putin he will reverse his opposition to imposing sanctions on a Russian natural gas pipeline to Europe, Nordstream 2, and declare the U.S. “will defend the people of Ukraine.”

“We can do that one way or another, it doesn’t mean we have to engage our men and women in uniform, but we will certainly be there to support,” she said.

With reporting by The Associated Press.

Joe Gould was the senior Pentagon reporter for Defense News, covering the intersection of national security policy, politics and the defense industry. He had previously served as Congress reporter.

More In Reagan Defense Forum