Iraq?s biggest Sunni political bloc committed itself on Sunday to talks with Shi'ites and Kurds to form a government of national unity, but said its key demands, including changes to the constitution, must be met. The United States, keen to drive the political process toward a stable consensus, wants the Kurds and majority Shi'ites, who dominated last month's elections, to form a government that includes minority Sunnis. It hopes an inclusive coalition will undermine the raging Sunni Arab insurgency.

Four policemen were killed and nine wounded by a roadside bomb in Baquba, 65 km (40 miles) north of Baghdad. Thirteen other people were killed in attacks across Iraq, including a policeman's four nephews who died when a rocket hit his home. The Iraqi Accordance Front, which comprises three mainly Islamist Sunni Arab groups, said it would appeal against the results of an election it believes was rigged but would still take part in talks on a new coalition government. ?It will be active in talks with other political blocs to form a unity government,? said Tareq al-Hashemi, whose moderate Iraqi Islamic Party is the biggest member of the Front.

Hashemi said the election results did ?not reflect the political and population weight? of the Front, which believes it should have won 11 more seats. The Sunni coalition would seek key ministries in the new government as compensation, he said. The Front also intends to hold Shi'ites and Kurds to a promise, extracted under US pressure, of reviewing the constitution approved in a referendum last October.

Many Sunnis fear the constitution's provisions for regional autonomy will give Kurds and Shi'ites control over Iraq's vast oil reserves and eventually break the country apart. ?We ask the blocs not to put obstacles in the way of making some changes to the constitution,? Hashemi told a news briefing. After boycotting parliament last year, Sunni leaders had hoped a big turnout in the December 15 election would put them in a strong position to press for amendments, particularly on a new federal state structure, which they fear could give control of oil to Kurdish and Shi'ite regions in the north and south.

They had also hoped that other Shi'ite and secular groups opposed to decentralization would undermine the dominance of the main Shi'ite bloc, the Islamist Alliance, whose most powerful leaders are strongly in favor of federal autonomy. But the success of the Alliance in coming close to retaining its majority may dampen Sunni hopes of securing amendments with the help of anti-federalist Shi'ites in parliament. A Western diplomat closely involved in Iraq's political process said Sunni ambitions may have to focus now more on influencing legislation to be enacted that will spell out exactly how autonomous regions can be established and operate.