Iraqi Prime Minister Nouri al-Maliki will return to power for another four-year term after Iraqi lawmakers working late into the night Wednesday agreed on a tentative deal to form a new government, lawmakers said.

The deal breaks an eight-month impasse that paralyzed the government, encouraged insurgent attacks and rattled potential foreign investors. The Sunni-backed secular coalition, which had vehemently opposed al-Maliki, finally resigned itself to serving in his government along with the other main political groups.

"Finally, fortunately, it's done. It's finished. All the groups are in it," said Kurdish lawmaker Mahmoud Othman, who took part in the nearly seven hours of negotiations Wednesday following talks the previous two days.

An official in the Sunni-backed coalition, Iraqiya, also confirmed the deal. He spoke on condition of anonymity because of the sensitivity of the negotiations.

The deal involves concessions to both the Kurds and to Iraqiya, which is led by former prime minister Ayad Allawi. U.S. officials have worried that a government without the backing of minority Sunnis could spell a return to sectarian warfare.

The White House welcomed the development.

"The apparent agreement to form an inclusive government is a big step forward for Iraq," said Tony Blinken, national security adviser to Vice President Joe Biden, the administration's point man for Iraq. "All along we've said the best result would be a government that reflects the results of the elections, includes all the major blocs representing Iraq's ethnic and sectarian groups, and that does not exclude or marginalize anyone."

But the return of al-Maliki to the premier's post underscores Iran's rising influence in Iraq at a time when American forces are leaving. It was Iran that engineered al-Maliki's recent endorsement by anti-American cleric Muqtada al-Sadr, who controls 40 seats in the new parliament. The two men, fellow Shiites, had been enemies in the past.

It was unclear what role al-Sadr and his hard-line Shiite faction might play in a new government — and whether al-Maliki's partnership with the Sadrists could derail pro-Western security and commercial policies.

One of the leaders of the Iraqiya coalition, Saleh al-Mutlaq, blamed Iran for al-Maliki's likely return to office.

"The pressure of Iran was too much," he said.

Lawmakers familiar with the negotiations described the general outlines of Wednesday's deal as follows:

Allawi's bloc will choose the parliament speaker. It was not known who that would be, but their pick was expected to be ratified when lawmakers meet Thursday for only the second time since the March 7 election.

The government will also create a new council with authority over security issues. That is intended as a concession to Allawi's coalition, which has pushed heavily for ways to reduce al-Maliki's power in exchange for offering its support.

But details apparently still need to be worked out, and it was not immediately clear that Iraqiya would end up controlling the council or that it will have real authority.

Allawi's bloc also won a concession to end the so-called de-Baathification law in two years, according to the Iraqiya official. The law regulates efforts to purge members of Saddam Hussein's former regime from government jobs. Sunnis detest the law because they consider it a thinly veiled attempt to keep them from power.

It was uncertain what role, if any, Allawi himself would play in the government. Othman said Allawi had signed off on the deal.

The Kurds, who have played the role of king-maker in Iraqi politics since the fall of Saddam, were granted their demand that President Jalal Talabani, a Kurd, keep his largely ceremonial job.

Unclear, though, is whether the Kurds won any other concessions. They had wanted firm guarantees in exchange for their support, including a referendum to decide control of the oil-rich region around Kirkuk. The area lies just outside the Kurds' semiautonomous zone, but they are part of a three-way contest for influence along with ethnic Turks and central authorities in Baghdad.

The marathon negotiating session began with Iraqiya demanding the presidency but swiftly seeing their choices narrow. The Iraqiya official said the Shiites came in assured of the prime minister's post and the Kurds held firm to the presidency.

"They offered Iraqiya the speaker of the parliament and said: `Take it or leave it,' " he said. "We did not have a choice, knowing full well they will form a government with us or without us."

U.S. officials tried repeatedly to get the Kurds to give up the presidency in favor of Allawi — but to no avail, a sign of waning American influence.

Ever since the election, Iraqi lawmakers have tussled back and forth over who would lead the new government. Iraqiya was able to capitalize on widespread Sunni frustration to get 91 seats in the election, compared to 89 for al-Maliki's bloc.

But despite Iraqiya's bragging rights as the victor, it was never able to find the political partners it needed for a parliamentary majority. That paved the way for al-Maliki, who had to make peace with bitter rivals among fellow Shiites.

Al-Maliki came from political obscurity four years ago when he was chosen as a compromise candidate to lead the country at a time when Sunnis and Shiites were battling in the streets. He presided over a return to relative stability.