LONDON — The ruling party in a northwestern province of Pakistan voted Monday to block NATO supply lines by Nov. 20 unless the United States stops its drone strikes in the nearby tribal belt.

The party, Tehreek-e-Insaf, which governs Khyber-Pakhtunkhwa Province, passed a resolution that threatened to block the supply lines through the region in response to a C.I.A. missile strike that killed Hakimullah Mehsud, the leader of the Pakistani Taliban, on Friday.

The death of Mr. Mehsud has set off a furious reaction from Pakistani politicians, particularly Imran Khan, the leader of Tehreek-e-Insaf, who with others said that the targeted killing had derailed incipient peace talks with the Taliban.

But Mr. Khan’s resolution stopped short of imposing an immediate blockade on NATO supplies. Setting the Nov. 20 deadline was a means of building pressure on the Pakistani prime minister, Nawaz Sharif, to end American drone strikes, while buying time to avoid a tricky confrontation with Mr. Sharif’s administration, which does not favor blocking NATO lines.