ISLAMABAD, Pakistan — A top opposition leader called on President Musharraf to step aside yesterday after his ruling party conceded defeat in parliamentary elections. The vote was also a slap to Islamist parties, which lost control of a province where Al Qaeda and Taliban fighters have sought refuge.

With counting from Monday’s election nearly complete, the two main opposition parties won a total of 154 of the 268 contested seats, according to the Election Commission.

The pro-Musharraf party trailed with 39 seats, and the group’s leader acknowledged the loss.

“We accept the election results, and will sit on opposition benches,” chairman of the Pakistan Muslim League-Q, Chaudhry Shujaat Hussain, told AP Television News. “We are accepting the results with grace and open heart.”

Although final official results are not expected until today, opposition parties were confident of victory and began mapping plans for a new government and a possible showdown with Mr. Musharraf. A former prime minister and leader of the opposition Pakistan Muslim League-N, Nawaz Sharif, recalled statements by Mr. Musharraf last year that he would step down only if he lost the support of the Pakistani people.

“He has closed his eyes. He has said before that he would go when the people want him to do so and now the people have given their verdict,” Mr. Sharif told reporters in Lahore.

The Pakistan People’s Party of assassinated ex-prime minister, Benazir Bhutto, was leading with 86 seats and was likely to spearhead the new government in partnership with other opposition groups.

Bhutto’s husband, Asif Ali Zardari, told reporters yesterday he would soon meet with Mr. Sharif and other opposition leaders “to form a government of national unity.” Mr. Zardari made clear he would not include politicians who had been allied with Mr. Musharraf.

“We will seek support from democratic forces to form the government, but we are not interested in any of those people who are part and parcel of the previous government,” Mr. Zardari said.

But Mr. Zardari carefully avoided an unequivocal statement about whether Mr. Musharraf should remain in power. The two main opposition parties were unlikely to finish with two-thirds of the seats required to impeach the president.

Mr. Musharraf’s spokesman, Rashid Quereshi, rejected suggestions the Pakistani president step down. Senator John Kerry, who met yesterday with Mr. Musharraf along with other American lawmakers, said the Pakistani leader expressed willingness to work with the new government. But the former general is so unpopular among the Pakistani public that opposition parties are likely to find little reason to work with him — particularly since he no longer controls the powerful army.

At best, Mr. Musharraf faces the prospect of remaining in power with sharply diminished powers even if the opposition fails to muster the two-thirds support in parliament to impeach him. Constitutionally, the president is the head of state and nominally the commander in chief of the armed forces. He also has the power to dissolve parliament.

But the prime minister runs the government on a day-to-day basis. With a strong electoral mandate, the new prime minister would doubtless command greater authority than those who served under Mr. Musharraf’s military rule. The White House, which has backed Mr. Musharraf because of his support for the war against terror, declined to comment until the final results were announced. But a State Department spokeswoman, Nicole Thompson, called the election “an important step on the path towards an elected, civilian democracy.”

Senator Joseph Biden, a Democrat who chairs the Senate Foreign Relations Committee and one of several American lawmakers who observed the election, said the results mean America can shift its Pakistan policy.

“This is an opportunity for us to move from a policy that has been focused on a personality to one based on an entire people,” Mr. Biden said, adding that Washington should encourage more deeply rooted democracy in Pakistan. Pakistani analysts said the results pointed to broad support for centrist, democratic parties at the expense of patronage politicians and Islamist movements.

The pro-Taliban Jamiat-e-Ulema party won only three seats in the national parliament. And a coalition of Islamist religious parties was poised to lose control of the regional administration in the North West Frontier Province, which it won in the 2002 elections.