The arrest of Mohammed Mohsen al-Zubaidi reflected U.S. determination to brook no interlopers in its effort to build a consensus for administering Iraq. Timed just before Monday's high-profile conference, it sent a clear message: Don't meddle. 

Al-Zubaidi was a returned exile associated with the opposition Iraqi National Congress who had declared himself mayor of Baghdad without sanction from U.S. occupation authorities. U.S. Central Command on Sunday accused him of "subversion." 

His activities, including designation of "committees" to run city affairs, had complicated the efforts of postwar U.S. civil administrator Jay Garner to reorganize political life. A U.S. military spokesman said al-Zubaidi was arrested "for exercising authority which was not his." 

Central Command accused al-Zubaidi and his associates of "obstructing the normal means of governance for their own self-interests," particularly by claiming control over the power company and other utilities. 

In a statement, the command said it warned al-Zubaidi to stop his actions. "He instead ... continued his subversive actions," it said. 

Monday's conference, second in a series likely to extend well into May, was expected to attract 300 to 400 delegates from political organizations that had opposed Saddam Hussein and from other Iraqi interest groups, said a Garner deputy, Barbara Bodine. 

The first meeting was held April 15 in Ur, in southern Iraq, just a week after U.S. troops took control of the Iraqi capital and ousted the Saddam government. Fewer than 100 Iraqis participated, many of them exiles, as some Shiites and others stayed away in protest of potential U.S. influence over selection of a new Iraqi president. 

But in a sign that Shiite resistance may be easing, one key Shiite group that shunned the Ur conference - the Iran-based Supreme Council of the Islamic Revolution in Iraq - indicated it might attend on Monday. 

"No definite decision has been taken so far. We have been invited and will most probably attend," leading member Mohsen Hakim told AP in Tehran. 

Bodine told reporters, "I think we are going to see more of an indigenous representation, simply because we've had more time to organize." 

"There's going to be a lot of leadership emerging," she said. No obvious presidential choice has appeared thus far, however, and Bodine would not be drawn out on names. "I wouldn't know today who that's going to be." 

In the Spanish capital, Madrid, a gathering of Iraqi exiles issued a statement calling for Iraq to be governed by a federal system that respects all religions, ethnic groups and women's rights. Their three-day meeting was sponsored by Spain's government, which was a staunch supporter of the U.S.-led attack on Saddam's regime. 

The conference in Ur agreed on a set of 13 principles, among them that Iraq must be democratic, Saddam's Baath Party must be dissolved and a future government should be organized as a federal system - the last point an acknowledgment of the difficulty of centrally governing a land and society divided between Sunni and Shiite Muslims, Kurds and Arabs. 

The series of conferences is to produce an "interim authority" led by a new president that would pave the way for a constitution and democratic elections two years or more in the future. 

British Foreign Office Minister Mike O'Brien also was to attend Monday's talks, saying his presence there is a sign of Britain's commitment to returning power to the Iraqi people as soon as possible. 

Shiites, a 60 percent majority long suppressed under Saddam's Sunni-dominated regime, have been enthusiastically exercising newfound freedoms, organizing community-level political activities, protests against the U.S. occupation and religious events. 

Open elections in Iraq might produce a government dominated by the Shiite clergy, as in neighboring Iran, some observers believe. But Defense Secretary Donald H. Rumsfeld insisted in an Associated Press interview last week, "That isn't going to happen." 

Rumsfeld, who is on a tour of the Persian Gulf, repeated that stand Sunday during an interview with Abu Dhabi television, which is widely seen throughout the Arab world. 

"We cannot have a regime like that in Iran where a few religious men control the situation in Iraq," Rumsfeld said. "The men and women of Iran want freedom and change. A regime like that of Iran is not compatible with our vision for Iraq." 

Some Shiites fear Washington will force a president on Iraq - Ahmad Chalabi, a longtime exile supported by U.S. government funds in building the Iraqi National Congress opposition group. 

Chalabi has attracted little public support inside Iraq. The government in neighboring Jordan warned Washington on Sunday against backing Chalabi, saying he lacked credibility among Iraqis and noting his 1992 conviction in absentia for fraud in Jordan. Chalabi has denied any guilt and said the case was instigated by Saddam. 

In other developments Sunday: 

-Central Command announced that Lt. Gen. Hossan Mohammed Amin, the Saddam government's chief liaison to U.N. weapons inspectors, was in U.S. custody, latest in a series of ex-officials who have surrendered or been captured. 

- A man shot at two U.S. military vehicles in downtown Baghdad, wounding four soldiers, one seriously. "There are still some small pockets of resistance in Baghdad," said a military spokesman, Capt. David Connolly. 

-Preliminary tests indicated a 55-gallon drum found with others near the northern Iraqi town of Baiji may contain a mixture of nerve and blister agents, Central Command said. 

-Radio broadcasts by coalition forces offered a reward to Iraqis who hand over antiquities stolen from Iraqi museums or provide information about the looters. 

Bodine, U.S. postwar chief for Baghdad and the rest of central Iraq, met Sunday with top bureaucrats from the previous city administration on how to "get everything up and running" in Baghdad. 

Everything remained far from "up" on Sunday. 

Only about 50 percent of Baghdad's electrical needs were being met, said Maj. Gen. Carl Strock, chief engineer for Garner's office. 

City power was cut by U.S. bombing in early April, and Strock said he could not predict when Iraqi crews would have full power restored. The power shortage has crippled Baghdad, idling pumps for distributing clean water and for treating sewage, giving looters the cover of darkness in some areas, and keeping most shops closed. 

Automobile traffic has built steadily for days, however, particularly because civil servants and other workers have been converging on former workplaces in hopes that offices will open - or at least that someone will pay them. 

In their talks with Iraqi officials, Bodine and her aides discussed making U.S. dollar payments to city workers to get critical services, such as garbage pickup, going again. 

"This meeting was a necessary one," said Sael Hussein, deputy mayor for technical services. "We discussed problems and solutions, and how to work together."