Iraq's largest Sunni Arab political bloc returned to the government fold Saturday after calling off a nearly one-year boycott of the Shiite-dominated leadership — another critical stride toward healing sectarian rifts.

The return of the National Accordance Front does more than politically reunite some of Iraq's main centers of power.

It was seen as a significant advance toward reconciliation and efforts to cement security cooperation between Shiite-led forces and armed Sunni groups that rose up against Al Qaeda in Iraq.

The United States has pressured Iraq's government to work toward settling the sectarian feuds, which brought daily bloodshed until recent months. The hope is that more parties staked in the future of Iraq could mean a quicker exit for U.S. and other foreign forces.

Iraq's sharply improved security situation is already bringing plans for a pared-down British force.

On a visit to Baghdad, British Prime Minister Gordon Brown said plans are being made to scale back troops in Iraq, but refused to consider an "artificial timetable" for withdrawing Britain's remaining 4,000 soldiers.

Brown's comments — following meetings with Iraqi leaders — come in advance of next week's scheduled address to British lawmakers on Iraq, when he is expected to give more details on troop reduction plans as insurgent attacks and militia violence drops sharply around Iraq.

No specific troop withdrawal figures have been made public, but a senior British military officer has predicted substantial troop cuts in Iraq next year.

"It is certainly our intention that we reduce troop numbers, but I am not going to give an artificial timetable at the moment," Brown said following talks with Prime Minister Nouri al-Maliki and President Jalal Talabani.

A departure of more British forces will have little bearing on the battlefield. The troops, mostly based outside the southern city of Basra, no longer have a combat role and are involved mostly with training Iraqi security units.

Britain's moves come about four months after Iraqi opened a major offensive in Basra to root out Shiite militias with suspected links to Iran.

The campaign — which began with disarray among Iraqi forces — ultimately gained ground with U.S. help and reclaimed wide control over Iraq's second-largest city and key oil center.

Although Britain maintains the second-largest foreign military force in Iraq, it is dwarfed by the approximately 150,000 U.S. soldiers currently in the country.

Brown's visit came on the eve of an expected stop by presidential candidate Barack Obama on the second leg of a tour of the Pentagon's war zones. Obama spent Saturday in Afghanistan and is later expected to hold talks around the Middle East and Europe.

Al-Maliki, meanwhile, called Obama's suggestion of a 16-month withdraw of U.S. combat troops as "the right timeframe."

In an interview with Germany's Der Spiegel magazine released Saturday, al-Maliki said he was not seeking to endorse the Illinois senator.

"That, we think, would be the right timeframe for a withdrawal, with the possibility of slight changes," al-Maliki was quoted as saying. "Those who operate on the premise of short time periods in Iraq today are being more realistic. Artificially prolonging the tenure of U.S. troops in Iraq would cause problems."

The break in the Iraqi political impasse came after parliament unanimously backed Sunni candidates to fill the post of deputy prime minister and head five midlevel ministries, including higher education and communications. Four other Cabinet posts were filled by Shiites.

The Front pulled its members from the 39-member Cabinet last August, complaining it was sidelined in important decisions. The political rift left al-Maliki's government without partners in bids to find common ground with Sunni leaders.

Sunni Arabs, who represent about 20 percent of the country, were highly favored under Saddam Hussein but the tables turned after his ouster when Iraq's majority Shiites held sway. The rivalries spilled over into a wave of sectarian killings and al-Qaida bombings apparently aimed at triggering civil war.

But Sunni sheiks last year began to organize militias — which came to be known as Awakening Councils — against insurgents. Their role has been considered key in undercutting al-Qaida and helping reduce violence to its lowest levels in four years.

"What happened today is a national step forward to boost the government's role and take the national reconciliation ahead," said the bloc's spokesman, Saleem Abdullah.

Petraeus, the top U.S. commander in Iraq, hailed the political pact as "a very important step forward."