WASHINGTON — A month before General David Petraeus and Ambassador Ryan Crocker deliver to Congress a make-or-break assessment of Iraq, the country’s prime minister announced a new ruling coalition that excludes the extreme sectarian parties that in recent months have left the government in protest.

The deal, which would align two of the three major Shiite parties with the two major Kurdish parties, is notable in part because it excludes Sunni parties, including the Iraqi Islamic Party led by the current Sunni vice president, Tariq al-Hashemi. A statement signed by Prime Minister Maliki, as well as leaders of the other major factions in the new coalition, said that they would be able to command a majority in the 275-seat parliament in Baghdad.

Yesterday the son of President Talabani, Qubad Talabani, whose Patriotic Union of Kurdistan will participate in the new alliance, told The New York Sun that no Iraqi political party was deliberately excluded from the compact.

“Anyone who is not in the coalition is not in the coalition by their own choice,” he said. “The members of this coalition have gone to great lengths to convince them to be part of this group to end this paralysis and it is unfortunate that people think they can hijack the political process. We must move beyond all or nothing.”

The fact that some political parties opted not to participate in the government could increase the chances for reconciliation down the road. Among the parties left out of the deal are both the Shiite faction loyal to Moqtada al-Sadr and the Sunni Islamist bloc known as Tawafuq. Both of those slates include parliamentarians and government officials that have worked openly with terrorists who have attacked Iraqi security forces and American soldiers, not to mention Iraqi civilians. One of the leaders of Tawafuq, Khallaf al-Ayan, has been implicated by American and Iraqi investigators in the April suicide bomb blast in the parliament. Mr. Ayan has denied the charge.

An independent legislator who has pressed for the arrest of both Sunni and Shiite terrorists, Mithal al-Alusi, yesterday told the Sun that the coalition was a good first step. “This is a good professional political step, but it won’t work if they don’t put professionals in the government,” Mr. Alusi said. “I hope this step will push the others to build a real political opposition. We need both a government and an opposition. But this is good because terrorists from Tawafuq and the Sadr side will not be in the government.”

So far, the agreement to form a political bloc does not mean the Iraqi ministries will change hands. The details on dividing up the ministries remains to be worked out. At the same time, the deal is a powerful prod to those Sunni politicians like Mr. Hashemi and a former prime minister, Iyad Allawi, to join the new coalition or risk an end to the political patronage they now enjoy in the current unity government.

That unity government fell apart last month after Tawafuq parliamentarians announced they were leaving the government. The Tawafuq walk-out followed a similar walk-out from Sadrist ministers, though not legislators, in the spring. Without a major Sunni presence inside the ruling coalition, already stalled political negotiations over an oil law and amendments to the constitution became impossible.

The political reconciliation in Baghdad is one of a series of benchmarks Democratic leaders in Congress have said they will look at to measure the progress of the military surge General Petraeus will be pushing to extend next month.

One military officer working closely on the Iraq strategy yesterday said the new coalition placed a band-aid solution on the crisis of the collapsed government. “For now this will stave off a legitimacy crisis and it gives the government something to do,” this officer said. “They have to cut pay checks and do some of the day-to-day stuff which is important.”

But this officer said that progress in provinces like Anbar and Baghdad neighborhoods in creating local governing councils has in some cases made the national government less relevant to reconciliation than it was envisioned it would be in 2006 after the 2005 elections.