Ryan Crocker, the U.S. ambassador to Iraq, told reporters he made the remarks today during talks with his Iranian counterpart, Hasan Kazemi-Qomi.
Crocker said that although Tehran has a stated policy of supporting a stable and democratic Iraq, Washington does not believe it is following that policy on the ground.
Crocker said that in the two months since the envoys' last talks, militant-related activity in Iraq attributed to Iran has increased, not decreased.
"We have laid out what is clear to us as evidence of Iranian support for some of these militia activities," Crocker said. "And again, for us, it is a very clear case. We have individuals in custody who have spoken of Iranian involvement. We have the evidence of weapons and ammunition captured on the ground."
Iran denies the charge and blames the U.S.-led invasion of Iraq in 2003 for the bloodshed between Iraq's majority Shi'a and minority Sunnis.
The two envoys held a first round of talks in May, the highest-level meeting between the two countries since 1980. Little progress has been noted.
Many observers have expressed doubts that this second round will make much progress, either.
Copyright (c) 2006. RFE/RL, Inc. Reprinted with the permission of Radio Free Europe/Radio Liberty, 1201 Connecticut Ave., N.W. Washington DC 20036. www.rferl.org