BAGHDAD, Iraq -- Hundreds of power workers shouting "No, no, to terror!" marched through Baghdad on Thursday to protest attacks that have killed dozens of their colleagues, while demonstrators in the south demanded that the new petroleum minister be from their oil-rich region.

The demonstrations came as negotiators for the two biggest factions in the new National Assembly worked out details of an Iraqi government that U.S. officials hope will pave the way for the eventual withdrawal of coalition forces.

Jawad al-Maliki, a negotiator from the Shiite-led United Iraqi Alliance, said talks had progressed enough for Shiite Arab and ethnic Kurd officials to agree to hold parliament's second session early next week, although no date had been set. The 275-seat National Assembly met March 16 to swear in its members.

"The negotiations were positive and very good," al-Maliki said. "In the coming days, the meetings will be continuous and decisive."

Lined up behind a black banner with the names of slain power workers, protesters demanded an end to attacks on electricity stations and oil pipelines -- targets in an insurgent effort to weaken the economy and undermine the U.S.-led coalition and interim government.

At the same time, in southern Basra, more than 200 workers gathered outside a local government building to insist that the new government's oil and transportation ministers be from that region.

Some oil workers threatened to disrupt production in the south.

"We will stop pumping the oil and go on strike for those working in the oil field and the ports if our demands aren't met," said Mohammed Abdul Hafez, a union official who was one of the demonstration's organizers.

The insurgency's persistent violence, and the threat of disruptions to Iraq's oil exports, have contributed to rising world crude prices over the past year.

Kurdish and Shiite negotiators debated Cabinet posts Thursday, and Abdul-Karim al-Anzi, a Shiite official, said lawmakers should be able to elect the president, two vice presidents and parliament's speaker in their session next week.

The prime minister is expected to be Ibrahim al-Jaafari, a politician from Iraq's Shiite Arab majority. Kurdish leader Jalal Talabani is likely to be named president.

One of the vice presidents will likely be a Sunni Arab, al-Maliki and al-Anzi said.

The move is an effort to reach out to the Sunni community, which is believed to be the backbone of the insurgency. Dominant under former dictator Saddam Hussein, Sunni Arabs mostly stayed away from Iraq's Jan. 30 election, some in a boycott of the vote and others in fear of attacks.

Shiite Arabs are estimated to make up 60 percent of Iraq's 26 million people, while Kurds and Sunni Arabs are each thought to be 15 percent to 20 percent.

The top U.N. envoy in Iraq, Ashraf Qazi, reached out to Sunni Arabs on Thursday by meeting with influential Sunni religious leaders at a Baghdad mosque.

Qazi "stressed the importance of ensuring that all components of Iraqi society are adequately represented in the constitutional making process," a U.N. statement said.

A visiting seven-member U.S. congressional delegation expressed optimism at the progress being made in forming a new government.

"We take hope home that our troops will be able to rejoin their families sooner rather than later," said Rep. Anna Eshoo, D-Calif.

After nightfall, a large explosion was heard near a joint U.S.-Iraqi military camp 25 miles north of Baghdad, followed by gunfire. U.S. military officials confirmed there was an attack, but no major damage was reported. No other details were available.

Earlier, in Rabia, police mistook some Iraqi soldiers wearing civilian clothes and carrying guns to be insurgents, and opened fire, killing three soldiers, police chief Ahmed Mohammed Khalaf said. The soldiers shot back, killing two police officers. Eight officers also were wounded in the gunbattle, which lasted about 10 minutes.

In the former rebel stronghold of Fallujah, police imposed a late-afternoon curfew in part of the city, shouting through loudspeakers: "Close your stores and go home!" They also set up checkpoints and searched cars. The curfew may have been related to a firefight earlier in the city's Jolan neighborhood between unidentified gunmen and Iraqi security forces.

Also Thursday, the U.S. military said a prisoner died the previous day at the Camp Charlie internment facility. The man, in his early 30s, was found lying in his cell and attempts to revive him failed, the statement said. It said the cause of death was under investigation.

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Associated Press writers Mariam Fam and Qasim Abdul-Zahra in Baghdad and Abbas Fayadh in Basra contributed to this report.