Embattled Pakistani Prime Minister Imran Khan on Thursday rejected opposition calls to resign and accused the United States of trying to topple his government as he faces a parliamentary no-confidence vote Sunday.

Opposition parties in the legislative National Assembly, or lower house of parliament, jointly submitted the no-trust motion earlier this month, seeking Khan's ouster for allegedly mismanaging Pakistan's economic and foreign policies.

The 69-year-old former cricket star said Thursday night in an address to the nation that he would not resign and would stand up to foreign intervention, rejecting the misrule charges by his opponents.

"The vote will take place on Sunday. Whatever the outcome may be, I will emerge stronger. I will not let this conspiracy succeed at any cost," Khan said in his address.

In what appeared to be a slip of tongue, the Pakistani leader named the U.S. as the origin of a "memo" that Khan said confirmed a "foreign conspiracy" prompted by his visit to Russia on the day President Vladimir Putin invaded Ukraine.

"We got a message from America — oh, not America, I mean a foreign country I can't name," Khan said in the live televised address.

"They say they are angry with Pakistan. ... They say they will forgive Pakistan if Imran Khan loses a no-trust motion. But if the vote fails, Pakistan will have to face serious consequences," Khan said, citing the text of the memo.

Journalists working for mainstream news channels in Pakistan have reported that the message in question was delivered to Islamabad's outgoing ambassador to Washington on March 7, a day before the opposition moved the no-trust vote in parliament.

"They [foreigners] were aware of the no-confidence motion before it was tabled [in parliament]. It means they [the opposition] were in touch with outsiders," Khan asserted, confirming the date on which the message was delivered to the Pakistani ambassador. He added that the alleged conspiracy was meant to punish him for pursuing an independent foreign policy for Pakistan.