Russia's President Vladimir Putin, who has always disliked what he considers U.S. attempts to influence events in his country, has mounted a steadily escalating attack on organizations that accept foreign money. (ALEXEY DRUZHININ/AFP/GETTY IMAGES)

President Vladimir Putin is expelling the U.S. Agency for International Development, the State Department said Tuesday, another in a series of ­ever-more-aggressive measures meant to limit the work of Russian activists who support democracy, protect human rights and promote fair elections.

The move closes a two-decade window, open since the end of the Cold War, that has allowed the American aid agency to operate fairly freely in Russia while providing $2.6 billion in assistance.

Putin, who has always disliked what he considers U.S. attempts to influence events in his country, has mounted a steadily escalating attack on organizations that accept foreign money — an attack that began during the Russian election campaign earlier this year and that hasn’t let up.

The amount of money that USAID provides to Russian organizations is not large — about $50 million this year, down considerably from the heights of the 1990s. But the expulsion is a very public slap at the United States that will give ammunition to those who view Russia as a major U.S. adversary.

The move will almost certainly further demoralize and isolate embattled Russian activists, with the heaviest weight falling on Russian organizations that have received U.S. support — groups that monitor elections, organize to deal with tuberculosis, advocate for human rights, defend the environment and work to improve education.

Victoria Nuland, a State Department spokeswoman, said the order was delivered in a letter to Washington last week.

No matter who wins the presidential election in November, the expulsion is likely to make relations with Russia even less of a priority for Washington than it has been in recent years, which might or might not suit Putin’s needs. The Obama administration has already come close to the end of its so-far-futile efforts to win Russian support for a joint policy on Syria.

‘A very bad signal’

A senior administration official said the USAID ouster did not necessarily mean the end of U.S. assistance. It was not immediately clear, for example, whether American money could be conveyed in other ways, without the oversight of USAID staff. “We are going to look for other ways to establish the general policy objectives we established at the beginning of the Obama administration,” the official said.

Some U.S.-government supported organizations will continue to work in Russia, including the National Democratic Institute, the International Republican Institute and the National Endowment for Democracy.

But Lilia Shibanova, the head of the election monitoring agency Golos, said the loss of USAID’s help suggested difficult days ahead. Golos was thrown out of its office and publicly vilified after Putin criticized the organization.

“This is a very bad signal,” she told the Ria-Novosti news agency Tuesday. “USAID has been our partner since 2002. I believe they have done a lot for Russian people, for the support of the human rights organizations and development of free journalism in Russia.”

The White House’s reset of relations with Russia nearly four years ago was based on finding areas of agreement where U.S. and Russian interests intersected, including Iran, Afghanistan and arms control. Human rights and civil society development have always been outside that framework.

Over the summer, the Russian parliament approved a law that requires nonprofit groups to register as foreign agents if they receive money from outside Russia to promote political ends. The definition of political ends was left vague. Several organizations that have been recipients of American money, including Golos, objected strongly to the law as a crude clampdown on them. Advocates pointed out that no conceivable Russian source of replacement funding exists.

A long-brewing decision?

USAID, which has been working in Russia since shortly after the fall of the Soviet Union, had budgeted $49.47 million for Russian programs for fiscal 2012, with 59 percent of that directed for programs supporting democracy and civil society, 37 percent designated for health projects and 4 percent for environmental programs. It had 13 American employees, supported by Russian staffers.

In commenting on the decision Tuesday, Nuland, the State Department spokeswoman, was careful not to directly criticize Russia. “This is a sovereign decision that any country makes, whether they want to have U.S. assistance through AID,” she said.

Matthew Rojanksy, an expert on Russia at the Carnegie Endowment for International Peace, said in an e-mail that he thought this decision had been brewing for a while.

“Russian authorities have made clear for the better part of a decade that they see Russia as a great power, and a provider of assistance, not a recipient,” he wrote. “Add to that tension over the pre- and post-election protests, which the Kremlin alleges were orchestrated by U.S.-funded NGOs, plus the deep disagreement over U.S. democracy promotion activities in the Middle East, and you can see why this decision may have come now.”

The expulsion was announced just more than a week after Secretary of State Hillary Rodham Clinton had seen Putin at an Asian security conference in Vladivostok.

Nuland said the State Department was informed of Russia’s decision on Sept. 12, just a few days after Clinton left. She said U.S. officials had indications that the move was coming during Clinton’s visit but did not get final word until later. She did not fully explain the nearly one-week delay in making the decision public; nor did she say why Russia had not announced its own decision first.

Interest within the U.S. government in Russian assistance programs has been waning for several years. Nuland alluded to that in describing the different approach USAID began to take after the financial recovery fed by high oil prices lifted Russia out of poverty. USAID typically no longer paid in bulk for programs but sought to work in a consulting role with local partners. The $50 million in this year’s budget is about half the average spent in Russia over the past 20 years — with most of the spending coming in the 1990s.

Lally reported from Tbilisi, Georgia. Will Englund contributed to this article from Vilnius, Lithuania, and Anne Gearan contributed from Washington.