Who is Muqtada al-Sadr?
(CNN) -- How has Muqtada al-Sadr gained so much attention?
Believed to be about 30 years old, al-Sadr is the son of a grand ayatollah and a man with a mission.
The firebrand cleric was little known outside Iraq before the U.S.-led invasion.
Now with fighters loyal to him holed up in Najaf's Imam Ali Mosque -- one of the most holy places in Shiite Islam -- he has become the focal point of anti-American sentiment.
Al-Sadr has promised to fight to the death against U.S. forces in Najaf.
"I will continue to defend Najaf as it is the holiest place. I will remain in the city until the last drop of my blood has been spilled."
These are powerful and symbolic words that resonate with the Shiite community, its history and tradition.
"It evokes the idea of the Karbala paradigm which is martyrdom, death, commitment, sacrifice and passion," says Akbar Ahmed, an Islamic scholar at the American University in Washington.
About 1,300 years ago, Imam Hussein uttered similar words before he battled his enemies in Karbala, knowing he would be killed but willing to die fighting.
Analysts say al-Sadr hopes to capitalize on Shiite emotion by drawing a skillful parallel between Iman Hussein's martyrdom and his own possible martyrdom in a fight against America.
He has even resorted to covering himself with white shrouds at Friday mosque ceremonies to say "I know I'm going to die," Amatzia Baram, a senior fellow of the U.S. Institute of Peace, told CNN.
According to Islamic tradition, the dead are buried in white shrouds.
Commentators have added that al-Sadr's move to take over one of the holiest sites in Shiite Islam is a very smart one.
"Al-Sadr is quite shrewd but also very crude," says Baram.
"He knows well the Americans will not charge, will not try to conquer it (the shrine) by force, so in a way he is using the holiest place for Shia as the body armor."
Moderate Shiite clerics say al-Sadr is not a spokesman of all Shiite and they do not approve of his methods.
But because of the symbolism he has chosen, they feel they have no choice but to stay silent.
"Even the so-called moderates of the Shiite community would feel very wary of attacking al-Sadr or seeming to criticize him," says Ahmed.
'I will keep on resisting'
The Imam Ali Mosque, with its golden bricks and dome, is in the center of Najaf's old town. It is a sprawling complex surrounded by walls more than 20 feet high.
The vast cemetery outside is one of the biggest in the world with as many as 2 million graves. It too has become a battlefield.
Al-Sadr -- who takes his spiritual direction from an ultra-conservative, exiled Iraqi cleric based in Iran -- is wanted on an Iraqi-issued warrant.
He is charged in connection with the brutal murder of a moderate Shiite cleric at the Imam Ali shrine in the early days of the U.S. occupation.
Followers of the maverick, whose father and cousin were each grand ayatollahs and assassinated by the regime of Saddam Hussein, launched attacks against the coalition in March when then-coalition administrator Paul Bremer shut down his newspaper.
U.S. military authorities allege the radical cleric used a six-week cease-fire to stockpile weapons and ammunition inside the shrine.
"I will keep on resisting and I am staying in Najaf and won't leave it till the last day of my life," al-Sadr said Monday.
"My stay is to defend Najaf, the holiest place."
According to al-Sadr, the situation in Najaf cannot improve until the United States leaves Iraq.
"In the present situation, democracy and occupation cannot be together nor freedom and occupation," al-Sadr said.
"Let us remove the occupation fist, then there will be freedom and democracy, but no democracy nor freedom with the occupation."
Al-Sadr has urged his armed supporters to keep up their battle even if he is seized or killed. The cleric has bastions of support in Baghdad and in many southern Iraqi cities.
CNN's Zain Verjee and John Vause contributed to this report