President Biden and other Western leaders have already threatened Russia with harsh sanctions if President Vladmir V. Putin moves troops into Ukraine. As tensions escalated this week, Mr. Biden warned the Russian president he would personally target him with sanctions if Russian forces invaded.

But how personal is personal?

The administration could move to seize an individual’s assets and bar travel to the United States by adding them to what is known as the Specially Designated Nationals list. But it is far from clear that such a move would matter to Mr. Putin.

Although he believed to have amassed a great deal of personal wealth, it’s highly unlikely that any of it is in the United States. And any wealth Mr. Putin has is not only well hidden from the Americans but within Russia as well, said James Nixey, the director of the Russia-Eurasia program at the Chatham House, a research organization in London.

“A lot of his personal wealth seems owned or safeguarded by his cronies,” Mr. Nixey said. When a controversy erupted over a palatial estate on the Black Sea said to belong to Mr. Putin, for example, the Russian billionaire Arkady Rotenberg stepped up to say he was the owner.

A travel ban, experts said, would also have limited impact.

“They can stop Vladmir Putin from vacationing in Disneyland,” said Jeffrey Schott, a senior fellow at the Peterson Institute for International Economics in Washington.

“These types of actions have been taken in the past against leaders of second-, third- and fourth-rate powers, not generally against major adversaries, because you still have to deal with them,” Mr. Schott said. “This is not going to change anything.”

All of this means, Mr. Nixey said, that “personal sanctions on heads of state are very difficult to do. What is more effective — even if slightly looser — is to target the people around him, the inner circle.”

Some of Putin’s inner circle, he said, clearly does have assets abroad, and they frequently travel, shop, send their children to school or live outside of Russia.“If his closest allies are not enjoying the type of life they want to lead,” Mr. Nixey said, that would put pressure on Mr. Putin over the longer run. But sanctions against members of this group have not been very harsh so far, he added.

“The West is playing of chicken right now,” Mr. Nixey said. “We’ve tried no sanctions, and fairly weak sanctions,” but not very tough ones.

Other penalties targeting Russia’s giant energy companies and banks would hurt more, but the pain could be felt even more sharply in Europe, which gets about a third of its natural gas from Russia.

“The question is whether the U.S. and Europe are ready to bear the cost of this,” said Marina Shagina, a visiting fellow at the Finnish Institute of International Affairs.