The volatile former mayor said though had received no intelligence reports of any US plan to undermine his presidency, he believed most ambassadors were in cahoots with the Central Intelligence Agency (CIA), which had a track record of meddling in other countries' affairs.

The Manila Times newspaper on Tuesday reported a former US ambassador to the Philippines had prepared a "blueprint to undermine Duterte", citing a document it had received from a what it described as a "highly placed source".

The US State Department has described the allegations as "false".

"Most of the ambassadors of the United States, but not all, are not really professional ambassadors. At the same time they are spying, they are connected with the CIA," Duterte said in a television interview.

"The ambassador of a country is the number one spy. But there are ambassador of the US, their forte is really to undermine governments."

Duterte has made no secret of his grudge against the United States and has a particular disdain for President Barack Obama, who he has told to "go to hell", mostly over Obama's concern s about Duterte's deadly drugs war.

He has made repeated threats to abrogate security treaties with the United States and vented almost daily about US "hypocrisy" and "bullying".

On Thursday, Duterte said he would honour those treaties and that he liked US President-elect Donald Trump and was keenly waiting for him to take office.

The Manila Times said Philip Goldberg, who recently ended his term as ambassador in Manila, had outlined various strategies over an 18-month period to destabilise Duterte.

That would include supporting the opposition and co-opting the media, the military, neighbouring countries and senior government officials to turn against Duterte and isolate him economically.

Duterte has a dislike for Goldberg and has previously called him a "gay son of a bitch". He referred to him in three successive live television interviews on Thursday, calling him Washington's "superstar" with a track record of trying to undermine governments.

Goldberg was expelled as ambassador to Bolivia in 2008 by then President Evo Morales, who accused him of siding with his rightist opponents and of orchestrating street protests.

The United States rejected that and said his expulsion was a "grave error".

"Maybe he will deny it but it's not good," Duterte said of Goldberg's alleged blueprint, which he said was plausible because of Goldberg's history.

He added: "You might be able to oust me, but I will give you a bloody nose."

Attempts by Reuters to reach Goldberg this week were unsuccessful.

US Assistant Secretary of State for East Asia and the Pacific Daniel Russel dismissed the Manila Times report.

"No such blueprint exists," he said in a statement on Tuesday.

"The United States respects the sovereignty of the Philippines and the democratic choices made by the Philippine people."