The Shiite religious leader in the central Iraqi city of Najaf denied issuing a fatwa (religious decree) calling on the populace not to impede coalition military forces, Arab news channel Al-Jazeera reported.
On Thurday, the US Central Command here said Grand Ayatollah Mirza Ali Sistani had issued such a fatwas.
Najaf is one of Shia Islam's most sacred sites, as the tomb of Imam Ali, the son-in-law of Prophet Mohammed, is located there.
As the only grand ayatollah of Iraq, Sistani is the most senior cleric for Iraqi Shiites. Some 95 percent of the country's population is Muslim, with Shiites making up more than half of that amount.
The regime of Iraqi President Saddam Hussein is dominated by Sunni Muslims, and the coalition has been hoping since invading the country that Shiites might rise up against the government.