Mr Sharif said Pakistanis were 'disappointed' with the talks outcome
Pakistani leaders have failed to reach agreement on restoring judges sacked by President Pervez Musharraf.
Pakistan's two main ruling parties wrapped up a weekend of talks in London without reaching a deal, officials say.
The issue is now unlikely to be resolved ahead of a self-imposed deadline on Monday, increasing the strain on the ruling coalition.
The junior party, the PML-N, will meet on Monday to consider whether to stay in the coalition, party officials say.
The party, led by former prime minister Nawaz Sharif, has already threatened to leave the cabinet.
"I think every Pakistani is disappointed with the outcome of these talks," said Mr Sharif.
"Despite very sincere efforts we have not been able to resolve the deadlock."
The new government had initially promised to restore the senior judges by the end of April but disagreed over how to do it.
Mr Sharif and the leader of the Pakistan People's Party, Asif Ali Zardari, have already held talks in Dubai on the issue.
After those talks, Mr Sharif announced that all the senior judges sacked by President Pervez Musharraf last year would be reinstated on 12 May.
Analysts say failure to resolve the differences have put the six-week-old coalition under strain.
Mr Sharif's party has campaigned for the unconditional reinstatement of the judges.
Mr Zardari has been wanting the reinstatement of the judges to be part of a larger package of constitutional amendments which would include reducing their powers.
President Musharraf sacked about 60 judges - some sitting on the Supreme Court - in November 2007, after declaring a state of emergency.
The Supreme Court had been due to rule on whether his re-election was legal.
They had also been due to rule on a controversial amnesty covering Mr Zardari and his wife Benazir Bhutto, who was later assassinated.