U.S. President George Bush says violence in Iraq is at its lowest level in four years, as the United States reduces the tour lengths of U.S. troops there.

The U.S. military in Iraq says coalition forces have killed six terrorists during operations Saturday. Four of the militants were killed south of Baghdad in an operation targeting an associate of al-Qaida in Iraq. Two others were killed in another operation near Samarra.

Iraq has met only three out of 18 goals set by Washington for political and security progress, according to a draft of a key Iraq report being prepared for Congress, The Washington Post reported on Thursday.

The United States has rejected an Iranian suggestion to hold higher-level talks on the security situation in Iraq. State Department spokesman Sean McCormack said he does not see talks between the U.S. and Iran at the level of deputy foreign minister at this time. McCormack said the two sides have already established a diplomatic channel between their ambassadors in Iraq.

Washington and Tehran agreed to set up a trilateral subcommittee on Iraq security on the first day of negotiations and will continue discussions at the expert level Wednesday, an Iraqi official told ISNA.

Envoys from the United States and Iran are holding a second round of talks on the security situation in Iraq, in a rare meeting between the two sides.

Iraqi Foreign Minister Hoshyar Zebari says Iran and the United States will hold a second round of talks on Iraq's security on July 24. Zebari said the ambassadors to Iraq from both countries will lead the talks in Baghdad.

Iraq's prime minister Saturday said Iraqi forces are ready to provide full security in the nation whenever U.S. troops leave. Nouri al-Maliki told reporters that Iraqi troops can assume complete responsibility for security at any time.

Iraqi and U.S. troops were holed up in residents houses under a curfew claimed to restore calm after days of internal fighting between insurgent groups in Sunni neighborhood in Baghdad.

U.S.-Iran talks about Iraq's security will begin in Iraq on May 28, Iran's foreign minister said Thursday, and kept up Tehran's call for foreign troops to leave. Manouchehr Mottaki said the negotiations would be exclusively about Iraq and that the first meeting, in the presence of Iraqi officials, would try to set a more detailed agenda.

Iraqi police say a car bomb explosion in a Shi'ite enclave in the restive Diyala province, northeast of Baghdad, has killed at least 32 people and wounded dozens more.

Iran's spiritual leader, Ayatollah Ali Khamenei, on Wednesday said he supported U.S.-Iran talks in Baghdad about improving Iraq's security, state-run television reported.