Pakistani Prime Minister Imran Khan said in a televised address to the nation on Thursday that he would not resign before a vote to oust him is held on Sunday.
Khan also said a "Western country" is backing his ousting because he visited Russia to meet President Vladimir Putin last month.
Khan faces a no-confidence vote from opposition parties seeking to oust him, and lost the numerical majority in the parliament after his main ally quit the government on Wednesday.
Indirectly accusing the US, Pakistan's longtime ally, of hatching a conspiracy to oust him for his "independent foreign policy," Khan blamed the opposition parties for being "stooges of the foreign power."
He further said: "On March 7, we received a letter from America. Okay, let's not name any country. We received a letter from a foreign country.
"It was an official document based on notes our ambassador took during a meeting with officials of that country, which says we will spare Pakistan if Imran Khan goes as result of the no-trust motion, otherwise it (Pakistan) will have to face the consequences."
Earlier in the day, Pakistan's National Security Committee (NSC) also condemned the purported communique from an unnamed foreign country, saying the language used was "unacceptable" and "undiplomatic."
The top civil-military body said the communication "amounted to blatant interference in the internal affairs of Pakistan by the country in question, which was unacceptable under any circumstances," according to a statement.
The combined opposition, led by the Pakistan Peoples Party and Pakistan Muslim League-Nawaz, submitted the no-confidence motion against Khan on March 8, and voting is expected to be held on April 3.
The ruling Pakistan Tehreek-e-Insaf has 155 members in the 342-member National Assembly and needs at least 172 lawmakers to hold power.
About two dozen of Khan's own lawmakers have also announced support for the opposition, which now claims to have a majority in the lower house of parliament and has called on the premier to step down.
Citing his latest trip to Russia, Khan said he was criticized for taking a "unilateral" decision to visit Moscow, but denied it. "I took the military leadership, the Cabinet, and even the former ambassadors. They all backed my decision."
He added: "My foreign policy is not against any country, including the US, in fact, it is for our own people."
