Can the U.S., a beleaguered superpower, still play leader of the free world?

Can an aging superpower still control the course of events in eastern Europe, where Russian troops are massing along Ukraine's border?

We're about to find out.

The United States is counting on new economic threats and old alliances to deter what it says is a possible plan to invade Ukraine by early next year.

It's tempting to write the Americans off.

After all, sanctions didn't make Russia leave Crimea in 2014. And the U.S. position has deteriorated since then on multiple fronts, at home and abroad.

Nowadays the U.S. is preoccupied with China. It not only left a fight with the Taliban, it pleaded for its foe to protect U.S. personnel on the way out of Afghanistan. And, this year, America's own democracy was nearly wrecked by internal divisions.

Banking, gas, weaponry

That brings us to the current standoff over Luhansk and Donetsk, areas in the Donbas region of eastern Ukraine on the border with Russia.

American intelligence says nearly 100,000 Russian soldiers have gathered nearby, and more are on the way, and Russia has prepared a series of other destabilization and disinformation measures to support an invasion.

The U.S. insists it has levers to pull and friends willing to help, setting the stage for a test of the Biden administration's broad belief in the value of alliances when standing up against authoritarians.

Tuesday — after Biden spoke for over two hours with Russia's Vladimir Putin, urging him to back off, and later with the leaders of four European countries — offered a better sense of what that might look like in practice with public appearances by two administration officials.

Biden's national security adviser said the warnings include bank sanctions tougher than anything the U.S. imposed after the invasion of Crimea.

"Things we did not do in 2014 we are prepared to do now," Jake Sullivan told a White House briefing.

Another administration official, Victoria Nuland, offered additional details as she testified before the U.S. Senate.

She said these sanctions would be applied in increments and the U.S. was already talking to allies about what to do after the first day, the fifth day, and the 10th day of an invasion.

The goal would be to make it difficult to move cash into, and out of, Russia.

"[We're talking about] isolating Russia completely from the global financial system. … Everything is on the table," Nuland told the Senate foreign relations committee.

"[The actions we're discussing are] extremely significant and isolating for Russia, and for Russian business, and for the Russian people."

Why might this matter to Putin? A longtime Kremlin foe, Bill Browder, has described bank-transaction freezes as Putin's Achilles heel, saying the Russian president has tens of billions of dollars stored abroad in the accounts of prominent oligarchs.

The U.S. is also trying to get Germany to join in a threat against Russia's cherished new Nord Stream 2 natural gas pipeline.

Germany's energy regulator has yet to approve the just-completed pipeline. The country's new foreign minister is a Green Party member who has previously expressed opposition to it, and new Chancellor Olaf Scholz has equivocated.

It's a tough dilemma for Germany. 

Natural gas represents one-quarter of all German energy consumption, almost all of that is imported, and Russia is a major supplier. 

Nord Stream 2 would carry volumes equivalent to more than half of Germany's total annual consumption of gas.

Asked whether the Germans are really willing to carry out this threat, Nuland said: "I believe they are." 

She said Russia's energy "cash cow" would be starved if Putin invaded Ukraine.

She urged Putin to focus on solving his own country's problems which are considerable given the above-average devastation COVID-19 has wreaked there. 

"Nobody wants or needs war at this moment. Least of all the people of Russia," she said.

"They don't want body bags coming home. They want better health care, better roads, better schools, better broadband ... I hope he thinks about what he owes his own people."

Biden: No plan to send U.S. troops

Nuland has a well-known history with Russia: In an earlier crisis in the region, the senior State Department official had a phone call surreptitiously recorded and posted online. 

The third threat from Washington: to send military equipment to help Ukraine. 

There is no talk of a U.S. troop deployment.  

"That is not on the table," Biden said Wednesday. "The idea that the United States is going to unilaterally use force to confront Russia invading Ukraine is not on, in the cards right now."

Americans are ambivalent these days about foreign engagements. 

In a recent U.S. poll, protecting democracy abroad was listed by respondents as the lowest on a list of 20 foreign-policy priorities.

But those same respondents ranked limiting Russian influence and maintaining a strong U.S. military as higher priorities.

Those mixed signals speak to a superpower undergoing unpredictable changes, at an unpredictable historical moment. 

That other concern: China and Taiwan

Biden made a symbolic pilgrimage before his meeting with Putin — to Washington's National Mall and the Second World War memorial.

It was the 80th anniversary of the Japanese attack on Pearl Harbor, which ultimately prompted the U.S. to declare war on its two great foes of the day, Japan and Germany.

A reporter at the White House news conference raised the possibility of a conflict involving its two modern-day foes.

To be clear, that's not just a nightmare scenario but enough of a real-world concern that U.S. policy-makers are preoccupied with both bits of it.

The same Senate committee that on Tuesday studied Russia possibly invading Ukraine will, one day later, hold a hearing about China and Taiwan.

Russia and China have both talked about reclaiming territory they consider theirs, and earlier this year together made a strategically timed show of diplomatic unity against the U.S.

So what would happen, the reporter asked Sullivan, if China and Russia moved on Taiwan and Ukraine at the same time — is the U.S. prepared to deal with that scenario?

Sullivan replied: "The United States is going to take every action we can take."