The Tehrik-e-Taliban Pakistan (TTP) at the beginning of March announced a month-long ceasefire. Later, it extended it for 10 days to give the fledgling peace talks a chance.
"TTP's central shura or council has unanimously agreed not to extend the ceasefire," the banned outfit said in a statement.
"However, the talks process will continue with complete sincerity and seriousness, and whenever a clear development comes from the government side, the TTP will not hesitate to respond with a serious move," it said.
TTP Mohmand Agency chief Umer Khalid Khurrsani also issued a statement saying the government was not serious about peace and the only way to implement true Shariah was jihad.
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The announcement came three days after Pakistan's Interior Minister Chaudhry Nisar Ali Khan said the peace process was about to enter a "comprehensive" phase.
He said the government would also release 12-13 "non-combatants" as part of confidence-building measures.
The Minister said the country would come to know about the comprehensive agenda of talks after the meeting.
Refusing to use the word "ceasefire", Khan said "cessation of violence" is in place but added that the government has intelligence reports that some groups within the Taliban is not too serious about the talks.
The Nawaz Sharif government had begun negotiations with the TTP through intermediaries in February to try to end the cycle of violence that has claimed over 40,000 lives.
Talks were a key campaign pledge for Sharif before he was elected to office for a third time last year.