LONDON — America and Iran engaged in heated exchanges yesterday as the American ambassador to Baghdad accused Tehran of intensifying violence against America’s military despite the fact the two countries have begun groundbreaking talks on Iraq.

At a bilateral meeting convened in Iraq’s government headquarters — only the second direct meeting in almost three decades — Ambassador Ryan Crocker clashed angrily with his Iranian counterpart, Hassan Kazemi Qomi.

Mr. Crocker presented evidence of Iranian support for Iraqi insurgents, including training and weapons responsible for the deaths of American troops, but Mr. Qomi responded that Washington’s charges did not withstand scrutiny.

“The two months since May have not exactly been encouraging,” Mr. Crocker said. “The fact is — and we made very clear in today’s talk — that over the roughly two months [since talks began], we have actually seen militia-related activities that can be attributed to Iranian support go up and not down.”

Iraq’s foreign minister, Hoshyar Zebari, said he saw signs of apparent progress at the session. “We have reached an agreement, for the first time, to work together on the security sub-committee for the benefit of the people of Iraq,” he said.

The two countries did agree to form a security committee with Iraq to focus on containing Sunni insurgents.

The committee would concentrate on the threat from groups such as Al Qaeda in Iraq, officials said, but not those militia groups that the American government accuses Iran of funding and training.

America’s military campaign to pacify Iraq is set to stretch into 2009 if a joint campaign plan formulated by Mr. Crocker and the top American commander, General David Petraeus, is accepted by Congress in September.

President Bush ordered five additional brigades to Baghdad in a phased deployment from January.