Baghdad, Iraq ? Militant Shiite Muslim cleric Muqtada al-Sadr ratcheted up his anti-American rhetoric Friday, threatening to launch suicide attacks if U.S. forces enter Iraq’s holy cities to capture or kill him.

Al-Sadr’s remarks, made during Friday prayers at the Kufa mosque, marked an ominous escalation in the standoff between the cleric, whose militia has seized control of mosques and other key sites in Najaf and Kufa, and U.S. officials who have been threatening to retake the southern cities by force.

Wrapping a white cloth over his shoulders to symbolize his readiness for martyrdom, al-Sadr urged the gathering of thousands of his followers to resist U.S. attempts to occupy the holy cities.

“We will shed blood to keep our holy city,” al-Sadr said.

He said that some of his followers had approached him, asking to carry out suicide missions against the United States. He told them not to do so at this time, he said, but he left open the possibility of future attacks.

“When we are forced to do so and when our city and holy sites are attacked, we will all be time bombs in the face of the enemy,” al-Sadr said.

In a televised speech on an Arabic-language channel Friday, L. Paul Bremer III, the chief U.S. administrator in Iraq, demanded that al-Sadr disband his militia.

“Armed militias should not be allowed to exploit holy shrines to advance personal political interests,” Bremer said.

Al-Sadr also chastised the citizens of Najaf and Kufa, many of whom do not support his occupation of their cities and have been closing their shops and leaving the area in anticipation of clashes with U.S. forces.

By contrast, al-Sadr praised the Sunni Muslim citizens of Fallujah, saying they “are ready to defend their city” against U.S. forces “until the last drop of blood.”

Al-Sadr’s public threat of suicide attacks is certain to further complicate efforts to reach a peaceful resolution with the United States.

Suicide attacks have been a particular problem in Iraq, killing hundreds since August.

Iraqi children, refugees from Fallujah, comfort each other after arriving at a makeshift refugee camp in the Khadra district of Baghdad, Iraq.