ISLAMABAD — Pakistan’s elections will be delayed six weeks until February 18 because of unrest following the assassination of Benazir Bhutto, authorities said today. Opponents condemned the postponement but said they would take part in the vote anyway.

The polls — seen as a key step in Pakistan’s transition to democracy after years of military rule — had been scheduled for January 8.

Bhutto’s Pakistan People’s Party believes the government is not sincere in holding fair elections, but the party’s central executive committee decided to take part in the polls anyway, a committee member, Nabeel Gabol, said.

The party of a former prime minister, Nawaz Sharif, quickly followed suit.

“We will not leave the field open for the king’s party under any circumstances,” a party spokesman, Ahsan Iqbal, said, referring to the ruling party, which is allied to President Musharraf.

The opposition alleged authorities were postponing the polls to help the ruling party, amid expectations that Bhutto’s group could get a sympathy boost at the polls. The ruling party could also suffer a backlash. Bhutto had accused elements within the group of plotting to kill her, a charge it vehemently denies.

It was not immediately clear if Bhutto’s party would pursue threats to take to the streets because of the delayed vote. Earlier, a party senator, Babar Awan, warned that the delay may trigger street protests and riots.