WASHINGTON -- The United States and Russia have expelled five diplomats and military attaches from each other's countries, U.S. officials said.

The latest expulsions, ordered by Russia on April 28, were of two American military attaches at the U.S. Embassy in Moscow. They were preceded by the expulsion of a Russian diplomat from Washington on April 22, the expulsion of a U.S. diplomat from Moscow on April 14 and the expulsion of a New York-based Russian diplomat on Nov. 6, 2007.

"I don't read much into the attache thing other than just the usual tit for tat," Defense Secretary Robert Gates told reporters at the Pentagon on Thursday.

"These things get into a kind of a back-and-forth, and at some point everybody decides to stop," he said.

The State Department disclosed the expulsions Thursday but shied away from drawing a link. Spokesman Sean McCormack said Russia had given the United States the reasons for the expulsions, but he declined to say what they were.

"We're not making any particular connection between the expulsion of these two individuals and any steps we might have taken," McCormack told a news briefing.

He said Russia's most recent action was "not justified" but that Washington would comply with the order. He also said Washington considered the matter closed.

"As far as we're concerned, we don't intend to take any further actions," he said. "We always reserve the right, but at this point I don't see that we're going to take any further action in response."

The relationship with Russia is very deep and broad, and "everybody feels we're able to do our diplomatic work despite these incidents," he said.

On Capitol Hill, the top U.S. diplomat for Europe, Daniel Fried, told a congressional hearing that he did not believe the expulsions signaled any deterioration in relations with Russia.

"We look at these incidents as something which happens from time to time in U.S.-Russian relations," he said. "It is not, in our view, the sign of some larger diplomatic struggle. It is not a sign of some downturn."

Fried also would discuss the reasons for the expulsions but, speaking earlier, U.S. officials said none of those involved had been declared persona non grata by either government and that none had been accused of specific wrongful conduct, such as espionage.

In Moscow, the Foreign Ministry declined to comment. The Russian Embassy in Washington also declined to provide any details, saying it never commented on the expulsion of diplomats.

AP, Reuters