A key coalition ally of Pakistani President Pervez Musharraf says it will withdraw its support unless the army crackdown in Balochistan is halted.
The Muttahida Qaumi Movement (MQM) says the government must begin talks with tribesmen in the restive province.
There has been a marked rise in violence as tribal groups push for greater political and economic rights.
Separately on Sunday a human rights team was fired upon as it travelled to Balochistan's troubled areas.
Analysts say a pullout by the MQM would not greatly alter the government's majority in the National Assembly but might affect the legislature in Sindh province.
Sindh is the MQM's stronghold. It has 42 legislators and is the largest party in the 167-seat provincial assembly.
Pakistan's army says it is only targeting "criminals"
A party statement said on Sunday: "If the government does not stop the current military operation in Balochistan by 13 January, the Muttahida Qaumi Movement will pull out of the government in protest on 14 January."
The party said the dispute with tribes people should be solved through negotiations not military action.
The army launched its crackdown after rockets were fired during a visit by President Musharraf last month.
Tribes people say 200 people have been killed since then, although the government has not confirmed any death toll.
Information Minister Sheikh Rashid Ahmed said the government would look at the MQM's "reservations and apprehensions".
He said he was confident the MQM would remain part of the coalition.
Tribes people and opposition parties say the government has used helicopter gun ships and air force jets against civilian targets in Dera Bugti and Kohlu.
The government says it is only targeting "criminals".
On Sunday a delegation of the Human Rights Commission of Pakistan was fired upon en route to Sui and Dera Bugti.
Chairwoman Asma Jahangir told the BBC the car she was travelling in was hit by two unknown gunmen in Punjab province, about 40km (25 miles) from the Balochistan border.