Also on Saturday, Prime Minister Gordon Brown of Britain made an unannounced visit to Iraq. He held talks with senior Iraqi officials in Baghdad, including Prime Minister Nuri Kamal al-Maliki and President Jalal Talabani, and then flew to the southern city of Basra to meet with British troops.

The Sunni ministers approved by Parliament were all members of Tawafiq, the largest Sunni bloc, which had been boycotting Mr. Maliki’s government since last August. The return of Tawafiq is a significant political victory for Mr. Maliki, who has been trying to cement his reputation as a national leader who transcends sectarian lines.

Sunni participation in the Iraqi government has been an important goal for the United States, and the return of the Sunni bloc will be seen as progress in an otherwise bumpy political reconciliation process.

Tawafiq’s decision to rejoin the Maliki government came after months of negotiations on a variety of interests important to Iraq’s Sunni minority.

“We have a written deal with Maliki,” said Abdul Kareem al-Sammarai, a member of the Iraqi Islamic Party, the largest party in Tawafiq. He did not give details. Under the agreement, Rafie al-Issawi, a Sunni who was minister of state for foreign affairs until the boycott began, will be Mr. Maliki’s deputy prime minister for security affairs. Other Sunnis will lead the Ministries of Culture, Communications, Women’s Affairs and Higher Education, and the State Ministry for Foreign Affairs.

Parliament also voted to endorse four members of the United Iraqi Alliance, the largest Shiite coalition, to replace ministers who were pulled by the political bloc led by the radical Shiite cleric Moktada al-Sadr. The Sadrists have been boycotting Mr. Maliki’s government since May 2007.

Along with members of other smaller political parties, most Sadrists refused to participate in Saturday’s parliamentary session.

Although the vote in Parliament appeared to put a definitive end to the boycott, Tawafiq has announced in the past that it was rejoining the government only to pull back.

In April, members of Tawafiq announced that they were working out a deal to return to Parliament. At the time, leaders said that the government was addressing some of their concerns by passing an amnesty law that led to the release of Sunni prisoners and by leading operations against Shiite militias.

Sunni leaders had also been pressing for a voice in security decisions and for the appointment of a Tawafiq member to head the powerful Planning Ministry. That ministry is led by Ali Baban, who left Tawafiq after the Sunni boycott began in order to keep his post.

The struggle over the Planning Ministry remains unresolved, said Khalaf al-Iliyan, the leader of the National Dialogue Council, a party within Tawafiq.

As for security, Sami al-Askari, a member of the United Iraqi Alliance, said Mr. Maliki considered Tawafiq’s demands for more say unconstitutional.

“He assured them that the Iraqi Constitution treated this issue clearly,” Mr. Askari said. “Security is overseen by the general commander of the security forces, and the prime minister is the general commander of the security forces.”

Tawafiq leaders acknowledged infighting about which parties within the bloc would get which ministerial posts.

As it turned out, four of the positions, including that of deputy prime minister, went to members of the Iraqi Islamic Party. Members of the National Dialogue Council were appointed to the other two posts. Mr. Askari said Ahl al-Iraq, a smaller party within Tawafiq, was promised other official positions.

Mr. Brown, at a news conference in Baghdad, said that his aim was to reduce the number of British forces in Iraq eventually but that he would not set an “artificial timetable,” echoing language long used by the Bush administration for American troops.

Mr. Brown visited on the eve of an expected trip to Iraq by the presumptive Democratic nominee, Senator Barack Obama, whose stated goal is to withdraw all combat brigades by the middle of 2010.

The legal basis for British and American troops to be in Iraq expires with a United Nations mandate at the end of December, and Britain, like the United States, is in the process of negotiating a new arrangement under which its forces would remain. A spokeswoman declined to comment on whether the new security pact was part of Mr. Brown’s discussions here.

Britain has about 4,000 soldiers in Iraq, down from 40,000 at the beginning of the war. Mr. Brown had said the current level would be sharply reduced this year, but his defense secretary postponed that cut in April.

Jock Stirrup, chief of the British defense staff, said in an interview with the BBC last Sunday that the reason for the delay was that the Iraqi Army unit that British soldiers had been training, the 10th Division, was moved out of the south and a new one would have to be trained.

British troops turned over control of Basra Province to the Iraqis in December, but they still have a base at the city’s airport, several miles out of town.

Suadad al-Salhy and Tareq Maher contributed reporting from Baghdad, and Nicholas Kulish from Berlin.