Pakistan President Pervez Musharraf has restated he will not let former PMs Nawaz Sharif and Benazir Bhutto return to Pakistan before elections this year.
The president is seeking an election deal, reports say
His two main political rivals have been out of the country during his rule.
Gen Musharraf's comments follow reports that he is negotiating a deal with Ms Bhutto's Pakistan People's Party (PPP) to broaden his support.
Observers say political violence in Karachi in which 41 people died over the weekend has put the deal in doubt.
President Musharraf has repeatedly rejected assertions by Ms Bhutto and Mr Sharif that they will return for the general elections due later this year.
But correspondents say he has been more ambivalent in recent months on the subject of Ms Bhutto's possible return - because of the reported deal-making that has been going on.
However, the president was unequivocal in an interview being broadcast on Friday.
"About their return before elections, no, there is nobody returning before elections," he told the private Aaj news channel.
His remarks came after weeks of growing protests against his rule, initially sparked by his suspension of the country's chief justice.
The president faces re-election by parliament and the country's provincial assemblies to stay in office when his current term runs out.
Correspondents say he wants to do so before the general elections, in which the PPP is expected to play a pivotal role.
Ms Bhutto has also said President Musharraf must keep a promise to stand down as army chief by the end of the year before a deal can be reached.
Her party dismissed President Musharraf's remarks as the "dying kicks of a vanishing dictator" and vowed she would return for the elections.
"General Musharraf himself is about to go, his days as the usurper president are over and it is just a matter of time before he has to quit," PPP spokesman Farhatullah Babar told the AFP news agency.
A spokesman for the faction of the Pakistan Muslim League which Mr Sharif leads also insisted he would return to Pakistan this year.
"There is no provision in the constitution which gives power to one man to bar a fellow citizen from entering the country," Raja Zafarul Haq told AFP.
Gen Musharraf's dual role as president and chief of army staff has been the cause of much controversy.
After he ousted Mr Sharif, who was prime minister, in a bloodless coup in 1999, Gen Musharraf was elected president in what observers say was an engineered referendum.
Mr Sharif was sent into exile in 2000, two years after Ms Bhutto had chosen to leave the country to avoid arrest on corruption charges.
More recently, her party is being seen as a possible ally for Gen Musharraf after the next elections.
The much reported political "deal" with the president is said to involve the PPP helping get him re-elected before the general elections.
But the BBC's Syed Shoaib Hasan in Karachi says the PPP appears to have reappraised its options following the violence in Karachi.
The PPP and other opposition parties fought pitched gun battles against the provincial ruling party, the MQM, which is part of Gen Musharraf's current ruling coalition.
Most of those killed were opposition activists, our correspondent points out.