Raising a new complaint about Iran, Defense Secretary Donald H. Rumsfeld on Tuesday accused Tehran of dispatching elements of its Revolutionary Guard to stir trouble inside Iraq.

At the same time, he rejected the idea that Iraq has slipped into civil war, asserting that media reports have overstated recent violence there.

Rumsfeld offered few details concerning his allegation of interference by Iran, which fought a nearly decade-long war with Saddam Hussein's Iraq in the 1980s and shares a largely unguarded border.

"They are currently putting people into Iraq to do things that are harmful to the future of Iraq," he told a Pentagon news conference. "And it is something that they, I think, will look back on as having been an error in judgment."

He did not elaborate except to say the infiltrators were members of the Al Quds Division of Iran's Revolutionary Guards, the network of soldiers and vigilantes whose mandate is to defeat threats to the 1979 Islamic revolution. The Al Quds Division is responsible for operations outside Iranian territory.

Rumsfeld and other U.S. officials have previously complained of Iranian complicity in the movement of explosives and bomb-making material across the border into Iraq, but Rumsfeld had not mentioned Iranian forces before.

He initially said the infiltrators were doing "things that are harmful to the future of Iraq," but later when asked specifically whether they were gathering intelligence or fomenting violence Rumsfeld said he did not know what their mission was.

Appearing with Rumsfeld, Gen. Peter Pace, chairman of the Joint Chiefs of Staff, said that although there have been indications of Iranian-manufactured weapons coming into Iraq, "the most recent reports have to do with individuals crossing the border." He said he had an estimate of the number but declined to reveal it.

Pace said he did not know whether the Iranians were sent by their government. Asked the same question, Rumsfeld replied, "Of course. Quds force, the Revolutionary Guard, doesn't go milling around willy-nilly, one would think."

Rumsfeld also was asked about violence in Iraq since an attack last month on a revered Shiite mosque touched off a wave of reprisals between religious sects.

"I do not believe they are in a civil war today," Rumsfeld said. However, he added, "There has always been a potential for civil war."

The secretary spoke nearly two weeks after the Feb. 22 bombing of a sacred Shiite shrine in Samarra, which was followed by the deaths of hundreds of Iraqis. Hoping to keep Iraqi efforts to form a unity government moving forward, U.S. officials have acknowledged concern about the violence but have repeatedly denied that they fear a full-scale civil war was erupting.

Rumsfeld acknowledged that the attack on the mosque had delayed efforts to form a government in which Shiites, Sunnis and Kurds would share power.

"Their efforts to fashion a unity government that will represent all elements of their society is clearly being delayed by the situation in Iraq," Rumsfeld said. But he also asserted that Iraqi leaders had thus far passed the test of holding the country together and containing insurgents' efforts to ignite a civil war.

"They have to be fully aware that if this does not work, they and all of the people who have supported them lose everything, if this turns into a civil war. They can't want that," he said. "My impression is they will sort through this and fashion a government of some sort" that rules from the center.