BAGHDAD, Iraq — A high-ranking American military officer yesterday described new details of allegations that Iran is meddling in Iraq, accusing the Islamic Republic of training Iraqi operatives to direct militants in their homeland.

The latest accusations, made during a news conference here, were part of a renewed drumbeat of American charges over Tehran’s role in Iraq following a period of faint improvement in relations.

Last week, after a visit to Baghdad by the president of Iran, Mahmoud Ahmadinejad, U.S. Army Lt. Gen. Raymond Odierno and Navy Adm. William Fallon accused his regime of destabilizing Iraq. Iran, meanwhile, claimed that America had reneged on an agreement to hold a fourth round of trilateral talks with Iraqi officials about security in Iraq.

Mr. Odierno, calling Iran the greatest long-term threat to Iraq, accused Tehran of trying to keep the Baghdad government weak for its own benefit. Mr. Fallon cited evidence that Iran continued to train and equip militants in Iraq.

Yesterday, a spokesman for American forces in Iraq, Rear Adm. Gregory Smith, fleshed out some of the details of those allegations. He said American troops recently discovered a cache of weapons south of Baghdad with markings indicating the arms had been made recently in Iran. He also alleged that Iran had been recruiting Iraqis for training in Iran, citing statements by Iraqi detainees. “Groups and elements,” including Iranians and militants attached to Lebanon’s Hezbollah militia, were training Iraqis in Iran to act as recruiters and trainers in Iraq, Mr. Smith said.

“They’re being trained as trainers to set up the teams inside Iraq,” he said along the sidelines of the news conference.

He said America gleaned the information from Iraqi detainees who had undergone such training late last year. He did not disclose further information, but vowed that more would be said in the coming weeks.

“All told the same story,” he said of the detainees. “Handlers trained by Hezbollah inside Iran came back here purposefully to support anti-coalition and anti-security elements.”

Security improved markedly in Iraq over the last six months of 2007, in part because of a dramatic decrease in activity by Shiite militias linked to Iran, which considers itself the patron to followers of the Shiite sect of Islam worldwide. But American officials, without disclosing numbers, have told reporters of a slight uptick recently in reported rocket and sophisticated roadside bomb attacks that they attribute to Iranian-backed militiamen.

Iran watchers say the Tehran government may be training and equipping a clandestine network of operatives in Iraq as a potential card to play against American forces in case Washington decides to attack Iranian nuclear facilities.

America and Iran have been locked in a nearly three-decade Cold War. Washington accuses Tehran of supporting Islamic militants across the Middle East and pursuing nuclear weapons under the guise of a civilian energy program.

In Iraq, dozens of American troops fell sick at bases using “unmonitored and potentially unsafe” water supplied by the military and a contractor once owned by Vice President Cheney’s former company, the Pentagon’s internal watchdog says, according to the Associated Press.

A report obtained by the Associated Press said soldiers experienced skin abscesses, cellulitis, skin infections, diarrhea, and other illnesses after using discolored, smelly water for personal hygiene and laundry at five American military sites in Iraq.

The Defense Department’s inspector general’s report, which could be released as early as Monday, found water quality problems between March 2004 and February 2006 at three sites run by contractor KBR Inc., and between January 2004 and December 2006 at two military-operated locations.

It was impossible to link the dirty water definitively to all the illnesses, according to the report.