Biden signals a tougher stance against Russia. Will it deter Putin from invading Ukraine?

U.S. President Joe Biden's move to put 8,500 troops on heightened alert for a potential deployment to Eastern Europe, along with a $200-million US shipment of defensive weapons to Ukraine, suggests the administration wants to signal it is taking a more aggressive approach toward Russia and the looming threat of a Ukraine invasion.

While some observers believe the U.S. president is on the right track and have praised his performance in handling this crisis, others say he has reacted too slowly and his recent actions may not be enough to thwart Russian President Vladimir Putin's military ambitions.

"The Biden administration has been incredibly slow in doing what I think is necessary to help Ukraine," said Bradley Bowman, senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies in Washington, D.C.

"I really do believe that the Biden administration should have been — at least since November — moving heaven and Earth to get Ukraine additional defensive weapons that it needs to defend its territorial integrity and national sovereignty."

Jim Townsend, a former U.S. deputy assistant secretary of defence for European and NATO Policy, said while it was understandable that Washington started off with a policy of not wanting to provoke Putin, that approach needed to end sooner.

"They certainly changed their tactics over the weekend at Camp David, that they're coming out now, showing a little bit more of a military muscle, with promises of more to come," he said.

Biden had met with top military officials at the presidential retreat, where several options were presented that would shift American military assets much closer to Eastern European countries bordering Russia, the New York Times reported.

"They have finally found, I guess, here in Washington, that it had gone on too long and they didn't want to be played for time," said Townsend. "And so they did get to change the tactic."

Tensions have long been simmering in the region, but hit a boiling point in December, when Russia had massed an estimated 100,000 troops near the Ukrainian border. As part of de-escalation talks, Russia has demanded that NATO deny membership to Ukraine, along with a reduction of NATO troops and weapons in former Soviet bloc countries.

On Wednesday, U.S. Secretary of State Antony Blinken said in a written letter delivered to Moscow that the U.S. has made no concessions to the main Russian demands over Ukraine and NATO. It rejected the call to permanently ban Ukraine from joining, and said allied deployments of troops and equipment in Eastern Europe are non-negotiable.

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However, U.S. proposals do include the potential for negotiations over the placements of offensive missile and military exercises in Eastern Europe, as well as a broad arms-control agreement. Blinken said he hoped to speak with Russian Foreign Minister Sergey Lavrov in the coming days.

Some Republicans have accused Biden of dragging his heels in response to Russia's military buildup, arguing that additional sanctions need to be imposed against Russia immediately.

"When it comes to pushing back against Russia, we need to show strength and not be in a position of doctrine of appeasement," Joni Ernst, a Republican senator from Iowa, recently told CNN.