The United States has no knowledge of whereabouts of Iraqi radical Shiite cleric Muqtada al-Sadr, White House spokesman Tony Snow said yesterday.

"It is unclear," Snow said on CNN. "He may be in Iran. It is pretty clear he is not holding press conferences and making his whereabouts known."

US military spokesman said last week that al-Sadr had left Iraq for neighboring Iran, although his supporters denied.

"All indications are in fact that he (al-Sadr) is in Iran and he left last month," Maj. Gen. William Caldwell told reporters.

The United States has been trying to press the Shiite-led Iraq government to aggressively crack down on the Shiite militia, particularly the Mahdi Army led by Muqtada al-Sadr.

Al-Sadr's militia is allegedly receiving money from Iran and blamed for much of the sectarian violence and is widely seen as the main threat to Iraq's unity.

Sadr's supporters dismissed the allegations that Sadr had left for Iran and insisted that he was "still inside Iraq and working normally without fear of US forces," Nassar al-Rubaie, head of Sadr's parliamentary bloc told reporters.