President Obama has broad executive powers to declare sanctions without approval from Congress, and he would most likely consider the next steps after Crimea votes in a referendum on separating from Ukraine, scheduled for Sunday, said Michael A. McFaul, until recently the American ambassador to Moscow. “It needs to be spelled out as explicitly as possible, either directly to Putin or to the two or three people who could talk to him about this,” he said.

Russia may be betting, as many analysts do, that the United States and its allies will not follow through with draconian sanctions, and has made it clear that it would respond harshly and asymmetrically. On Friday, Gazprom hinted that it might cut off gas exports to Ukraine over unpaid bills, as it did in 2009, and an unnamed Defense Ministry official told Russian news agencies that it would consider stopping international inspections of its nuclear weapons.

Russia’s tycoons have been silent since the crisis began, apart from approving messages on social media. Many inside Russia’s large corporations are no doubt supportive of Mr. Putin’s moves in Crimea, which are widely seen here as correcting a historical error made by the Soviet leader Nikita S. Khrushchev, when he transferred Crimea to the Ukrainian Soviet Socialist Republic. Mr. Putin’s approval ratings are at their highest point since he returned to the presidency in 2012. If corporate leaders are complaining, they are doing it quietly.

“Of course they’re upset, but it doesn’t mean they are prepared to challenge Russia’s foreign policy,” said Mikhail E. Dmitriyev, an economist whose research group, the Center for Strategic Research, was originally founded to shape Mr. Putin’s economic platform. “This is a new reality. Even if somebody has reservations with regard to the policy’s effectiveness, I strongly doubt they would express it. This is a policy which, for the moment, is backed by the vast majority of the public. It’s not an exaggeration.”

In private conversations, though, several people described high anxiety within corporations, especially about the prospect of any sanctions’ affecting banks. Large Russian corporations have significantly increased foreign borrowing in recent years, and 10 were negotiating loans when the crisis boiled over, said Ben Aris, the editor and publisher of Business New Europe. Financial sanctions could set off a chain reaction of blocked transactions, frozen accounts and bank closings. “Those oligarchs who are already having trouble would be completely cut off,” he said.

Sberbank, the state retail bank, and the state investment bank VTB have actively expanded into Eastern Europe, including Ukraine, and own assets in Western Europe and the United States. Rosneft, the state oil company, has a deal with Exxon Mobil to drill in the Russian Arctic, the flagship project of Igor I. Sechin, a deputy prime minister and one of Mr. Putin’s closest aides.

Some pointed to a more long-term danger that the conflict over Ukraine, if it escalated, could culminate in a turn toward isolation for the Russian economy.