Russia took its first steps on Friday to retaliate against proposed American sanctions for Moscow’s suspected meddling in the 2016 election, seizing two American diplomatic properties and ordering the United States Embassy to reduce staff by September.

The moves, which Russia had been threatening for weeks, came a day after the United States Senate approved a measure to expand economic sanctions against Russia, as well as against Iran and North Korea. The bill, mirroring one passed by the House on Tuesday, now goes to President Trump for his signature.

The latest move by the Kremlin strikes another blow against the already dismal diplomatic relations between the two sides, with each new step moving Moscow and Washington farther from the rapprochement anticipated a few months ago.

Some analysts suggested that matters could get even worse. “Russia’s response to the new sanctions was inevitable,” Aleksei Pushkov, a legislator and frequent commentator on international affairs, wrote on Twitter. “There is a high probability that this will not be the end of it.”

The number of American targets inside Russia for Kremlin retaliation are limited, particularly if Moscow is worried about damaging the investment climate or about other economic fallout.

External arenas, however, are a different matter. Moscow might have shown some restraint in eastern Ukraine or in Syria because of the expectation of improving ties with Washington, but now, the Kremlin might be looking for places to challenge the United States.

Referring to the vote by Congress to toughen the sanctions, the Russian Foreign Ministry said in a statement: “This yet again attests to the extreme aggressiveness of the United States when it comes to international affairs.”

Dmitri S. Peskov, the spokesman for President Vladimir V. Putin, said the Russian leader had approved the retaliatory measures despite saying a day earlier that he would wait for the final version of the law before taking any such steps.

The version that emerged from the Senate vote late Thursday seemed to be the final one, Mr. Peskov noted, and the White House has already suggested that it might reject this law in favor of something even more onerous.

“The White House said that the bill could be toughened, so it doesn’t change the essence of the situation,” Mr. Peskov said.

It is unclear whether Mr. Trump will sign the legislation. But given the congressional investigations into possible collusion between his campaign and the Kremlin, and considering that the Republican Party has majorities in the House and the Senate, he is under considerable pressure not to use his veto.

The White House has been ambivalent about whether Mr. Trump will give his approval. During his campaign for the presidency, Mr. Trump pledged to improve ties with Russia.

The United States Embassy in Moscow issued a short statement confirming only that it had received the notification from the Russian Foreign Ministry and that it was sending the orders to Washington for review. The American ambassador, John F. Tefft, had expressed “his strong disappointment and protest,” the statement said.

The statement from the Russian Foreign Ministry said that the United States Embassy was asked to reduce its diplomatic and technical staff members in Russia to 455 by Sept. 1, matching the number of Russian diplomats in the United States.

In addition to the embassy in Moscow, the United States has consulates in St. Petersburg, Vladivostok and Yekaterinburg.

It was not immediately clear how many American workers would have to leave, because the Kremlin’s announcement did not detail which employees were to be included in the count. There are hundreds of staff members in Russia, including workers constructing an embassy building in Moscow.

Starting on Aug. 1, Russia will also block access to a warehouse in Moscow and to a bucolic site along the Moscow River where staff members walk their dogs and hold barbecues.

In December, President Barack Obama expelled 35 Russian diplomats and seized two estates, one on Long Island, N.Y., and one on Chesapeake Bay in Maryland, in response to Russia’s meddling in the United States presidential election.

Moscow did not respond at that time, with President Vladimir V. Putin signaling that he was hoping for better relations under the future President Trump. The chances of that happening have largely evaporated.

On Thursday, while expressing annoyance, Mr. Putin said at a news conference in Finland that he would wait to see the final law on the new American sanctions before deciding on a response. But the Senate vote tipped the balance, Mr. Peskov said.

The announcement from the Russian Foreign Ministry said that if the United States responded to the latest measure with any further expulsions, Russia would match them.

The White House has lobbied against the law containing the extra measures, calling it a curb on presidential power, because it would effectively force Mr. Trump to seek congressional approval before lifting any sanctions. The fact that it passed a Republican-controlled Congress underscores the unease in Mr. Trump’s own party about his repeated praise of Mr. Putin and of Russia.

The new law would strengthen sanctions first directed against Russia in 2014 after the annexation of Crimea and the destabilizing of Ukraine. Those sanctions curbed American involvement in the oil industry and limited Russian access to Western financial markets. Russia responded with a broad ban on Western food imports.

The new legislation would expand some of the measures, particularly in the energy market. European countries have expressed concern about the law’s potential impact on the energy market on the Continent, because it might affect the expansion of the Nord Stream pipeline that carries Russian natural gas to Germany under the Baltic Sea.

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