State Department deputy spokesman Tom Casey was reacting to Iran's announcement it will not hold a fourth round of security talks with the United States as long as US forces continue attacking Shiite militias in Baghdad.
"It's meaningless to have talks on anything with Iran as long as they don't change their behavior," Casey told reporters.
"That said, we continue to be willing and ready and are willing and ready to have additional discussions through this tripartite channel" with the Iraqi government, Casey said.
In previous security talks, Casey said, the United States has raised "the unhelpful behavior" of Iran towards Iraq in which it allegedly funds, trains and offers material support to militias.
Iran, whose ties with Washington have been severed since 1980 and which wants US troops to leave Iraq, strongly denies the allegations.
Even though the Iranians proclaim during these talks to support a stable Iraq, Casey said, "they have done nothing to address the fundamental problems that we and the Iraqis have."
In Tehran, Iran's foreign ministry spokesman Mohammad Ali Hosseini told reporters that there was no point in having talks with the United States while "we are witnessing open bombings by the US occupying forces in Iraq."
Iran and the United States held three rounds of talks on Iraq last year despite mounting tensions over the Iranian nuclear program. The talks have been stalled amid controversy over Iran's role in its conflict-torn neighbour.
The United States has in recent days carried out deadly rocket and air strikes against Shiite militants loyal to Iraqi cleric Moqtada al-Sadr in their stronghold of Sadr city in Baghdad.
