MOSCOW — Russia suspended participation in a key European arms control treaty Saturday, saying it will halt NATO inspections of its military sites and no longer limit the numbers of its tanks and other heavy conventional weapons.

The move, threatened for months, added new tension to relations with the West already strained over American plans to build a missile shield in Eastern Europe, Russian conflicts with its neighbors and Western criticism of Moscow’s human rights record.

Experts said the move was a symbolic gesture rather than a sign of Russian intent to build up forces near its borders. The Kremlin, they said, appeared to be expressing its dissatisfaction with the perceived American domination of global affairs, and positioning Russia as an unyielding global player.

The Conventional Forces in Europe Treaty was signed by Russian and NATO members in 1990, when Soviet and NATO troops faced off in Central Europe. It was amended in 1999 to reflect changes since the breakup of the Soviet Union, adding the requirement that Moscow withdraw its forces from the former Soviet republics of Moldova and Georgia.

Russia has ratified the amended version and slowly moved to withdraw its forces in recent years. America and other NATO members have refused to commit to the revised treaty until the withdrawal is complete.

Russian President Putin signed a decree freezing participation in the treaty that cited “extraordinary circumstances … that affect the security of the Russian Federation and require immediate measures,” the Kremlin said in a statement.

A Kremlin spokesman, Dmitry Peskov, told The Associated Press that Russia could no longer tolerate a situation where it was complying with the treaty but its partners were not. He expressed hope Russia’s move would push Western nations to ratify the updated treaty.

“Russia continues to expect that other nations that have signed the CFE will fulfill their obligations,” Mr. Peskov said.

The suspension will take place 150 days after Russia officially notifies all the countries concerned of its intention.

“We’re disappointed Russia has suspended its participation for now, but we’ll continue to have discussions with them in the coming months on the best way to proceed in this area — that is in the interest of all parties involved and provides for security in Europe,” U.S. National Security Council spokesman Gordon Johndroe said.

In Brussels, a NATO spokesman, James Appathurai, said: “NATO regrets this decision by the Russian Federation. It is a step in the wrong direction.” Britain’s Foreign Ministry also expressed concern.

The treaty is seen as a key element of maintaining stability in Europe. It establishes limitations on countries’ deployment of tanks, armored combat vehicles, artillery, attack helicopters and combat aircraft.

Withdrawal from the treaty would allow Moscow to build up forces near its borders. But Russian military analysts have said Russia’s move was a symbolic raising of the ante in the missile shield showdown more than a sign of impending military escalation.

Russian officials have strongly protested American plans to build a radar site in the Czech Republic and missile interceptors in Poland, saying the American system is aimed at its nuclear arsenal, and would upset the balance of strategic forces in Europe. America insists that the anti-missile system is aimed at future nuclear threats from Iran.

A respected military analyst with the online publication Yezhenedelny Zhurnal, Alexander Golts, said the moratorium probably won’t result in any major buildup of heavy weaponry in European Russia, because the country faced no real military threat and plans no attack of its own.

“It doesn’t make sense, and let’s be frank, Russia has no resources for it,” he said.

A Moscow-based defense analyst, Pavel Felgenhauer, said the end of inspections and checks by NATO countries will be the primary consequence of the suspension for many European nations, which rely on the inspections to keep track of Russian deployments.

For America, the moratorium will mostly be a symbolic gesture, he said, since America has an extensive intelligence network that keeps close track of Russian forces.

But the suspension will still be seen as an unfriendly move in Washington and Europe, Mr. Felgenhauer said.

“This will be a major irritant,” he said. “It will seriously spoil relations. The kind of soothing effect from the last summit with Putin and Bush will evaporate swiftly,” he said referring to a summit between Mr. Putin and President Bush this month at the Bush family vacation home in Kennebunkport, Maine.

The editor of Russia in Global Affairs magazine, Fyodor Lukyanov, said the Kremlin’s move was a step toward asserting Russia’s international resurgence.

He said that he expects the Kremlin to seek a reconsideration of all the treaties and agreements reached during and after the Soviet breakup, when Moscow was weak.

“It is a strategy to change Russia’s positioning on the world arena,” he said.

The Kremlin-connected head of the Moscow-based Institute for Political Research, Sergei Markov, said the move to impose a moratorium on the CFE was the Kremlin’s signal that Russia will not be bullied.

“There are people who don’t want Russia getting up from its knees, who are pushing it back, who are saying ‘You are weak, you lost,’ but Russia is resisting that,” he said.