US President-elect Donald Trump has invited Philippine leader Rodrigo Duterte to the White House next year during a "very engaging, animated" phone conversation, according to a Duterte aide.

Trump's brief chat with Duterte comes during a period of uncertainty about one of America's most important Asian alliances, marked by Duterte's hostility towards the US and his repeated threats to sever decades-old defence ties.

The call lasted just over seven minutes, Christopher Go, Duterte's special adviser, announced on Friday.

Trump's transition team had no immediate comment.

In his five months in office, Duterte has caused a stir by criticising the US, cursing President Barack Obama, making overtures towards China and pursuing a new alliance with Russia.

His diplomacy has created nervousness among some Asian countries, wary about China's rising influence and America's staying power as a regional counterbalance.

READ MORE: Duterte, Trump and Philippine-US relations

Duterte has praised China and told Obama to "go to hell" and called him a "son of a bitch" whom he would humiliate if he visited the Philippines.

The anger was unlocked after Obama expressed concern about possible human rights abuses in Duterte's war on drugs.

Duterte had initially expressed optimism about having Trump in the Oval Office, saying he no longer wanted quarrels. But it has not tempered his rhetoric and he has continued to rail at what he calls US "hypocrisy" and "bullying".

In an interview with Reuters news agency during the election campaign, Trump said Duterte's comments showed "a lack of respect for our country".

'Trump of the East'

Sometimes referred to as the "Trump of the East" because of his blunt remarks, Duterte has threatened repeatedly to sever US-Philippine defence ties, saying he "hates" having foreign soldiers in his country.

Joint military exercises look set to be scaled back next year, as Duterte demanded, including the number of US troops involved.

Philippines' Duterte welcomes Trump presidency

A question mark hangs over a defence agreement, which allows US forces access to Philippine bases on a troop rotation basis.

A source who has advised Trump's transition team on security policy told Reuters news agency last week that Trump would start a "clean slate" with the Philippines.

"He is perfectly capable of talking to Duterte in an open way without being wedded to previous policy failures," the source said of Trump.

Duterte caused a stir when he visited China in October and announced his "separation" from the US.

He has said the US could not be trusted to support the Philippines if it were attacked, as mandated in a joint defence treaty.

Some experts, however, say Duterte's appointment of special envoys to Washington suggest that despite his hostility, he intends to keep good ties.

Among those envoys is Jose Antonio, a multimillionaire property tycoon who bought the rights to name a new office tower in Manila "Trump Towers".

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Source: Agencies