The leaders of Pakistan's opposition coalition today formally rejected Prime Minister Zulfiqar Ali Bhutto's terms for a dialogue and said he had shut the door to negotiations to solve the constitutional crisis that has led to widespread violence since the March 7 general elections.

The decision of the general council of the Pakistan National Alliance was not unexpected, but it markedly increases the atmosphere of confrontation in this already tense and divided country.

The Alliance refuses to accept the results of the election, which Bhutto's Pakistan People's Party won by a landslide, on the ground that it was rigged. A civil disobedience campaign has been marked by clashes.

The pro-government press had called this the opposition group's chance, and the Alliance leaders said they were expecting the worst. "We could all be arrested tonight," said secretary general Ghafur Ahmed following today's meeting.

Many leaders were leaving Lahore, after three days of meetings here for their homes in other cities. "It is quite likely that Bhutto may try to crush this movement now," said another Alliance leader, Sidar Sherazbaz Mazari, as he prepared to leave for Karachi. "I only hope I have time to go home and pack a bag."

He added, however, that he thought arresting the opposition leadership would only make things worse for Bhutto in the long run.

Charges that the elections - in which Bhutto's party won 155 seats to the opposition's 35 - were rigged have gained wide acceptance throughout Pakistan.

In today's letter to Bhutto, which was addressed to him as leader of his party rather than as prime minister, the Alliance repeated three often stated demands: that Bhutto resign, that a new election commission be named and that fresh elections be held as soon as possible.

A second letter was sent to Pakistan's president, Chaudhry Fazal Elahi, asking him to use his constitutional powers to implement their demands.

Bhutto has said that it is not possible under the constitution to hold fresh elections, but added that he is prepared to enter into a dialogue with the Alliance. An election commission has been empowered to order new elections in constituencies where fraud can be proved.

Privately, Alliance leaders say, intermediaries have offered them another 40 seats and the reholding of provincial elections the Alliance boycotted following; the general elections. They say, however, that Bhutto has not made this offer formally.

The Alliance insists that if the election was rigged, new elections should be held. Today's letter to Bhutto said that the only possible "dialogue" would be over how to arrange new elections.

Bhutto has gone to great pains to show that he is being moderate and reasonable by offering the Alliance a chance to negotiate. But the opposition claims that since Bhutto has already "shut the door" on any question of new elections his reasonableness is only a sham.

Few observers here believe that it would be politically possible for Bhutto to give in to the Alliance's demands, but his political versatility is respected even by his enemies.

Mazari, the head of the National Democratic Party an important element in the opposition coalition - said in an interview today: "Rigidity and the spirit of confrontation does exist on both sides. Bhutto is not willing to give up and we say we represent the people of Pakistan and will not back down on this issue. If we accepted to bargain with Bhutto over this we would shatter our standards."

According to Mazari, the protest movement would only get worse if Bhutto locks up the leaders. Even if the end result were a military take over, which the Alliance opposes, Mazari said, this would at least get rid of Bhutto and pave the way for an eventual free election.

In the meantime, the Alliance members are refusing to take their seats when the National Assembly convenes Saturday and they have called for a nationwide general strike and a "day of mourning, a day of grief, a day of calamity."

Alliance secretary general Chafur AHmed said that the top leadership is not calling for demonstrations and processions, but is not forbidding them, either. provincial committees are free to organize what they like on Saturday, he said.