United States President Donald Trump has invited President Rodrigo Duterte to visit Washington as the alliance of the two countries "is now heading in a very positive direction," the White House said.

Trump called up Duterte Saturday night while the latter was hosting a gala dinner for the leaders of the Association of Southeast Asian Nations in Pasay City.

"President Trump also invited President Duterte to the White House to discuss the importance of the United States-Philippines alliance, which is now heading in a very positive direction," the White House said in a statement.

Duterte previously declared Manila would distance itself from Washington after former US President Barack Obama and his administration criticized the Philippines' bloody war on illegal drugs.

Duterte even threatened to abrogate the Enhanced Defense Cooperation Agreement between the two countries.

But when Trump won in the 2016 elections, Duterte made a phone call on him to congratulate him for his victory.

Saturday night's phone call, which lasted for about 17 minutes according to sources, was the two leaders second phone conversation.

Presidential Spokesperson Ernesto Abella, who released a statement also regarding the phone conversation of the two leaders, did not say if Duterte accepted Trump's invitation to the US.

The White House described the conversation between Duterte and Trump as "friendly."

The two leaders discussed the concerns of the ASEAN regarding regional security, including the threat posed by North Korea, Washington said.

North Korea has been engaged in ballistic missile launches in the past weeks, prompting America to send its aircraft carrier to the waters near the Korean Peninsula where it started conducting exercises with the South Korean navy.

Prior to his phone conversation with Trump, Duterte, in a press conference Saturday night, said he would ask Trump to ensure that a war would not break out in the region due to the situation in the Korean Peninsula.

The two leaders also discussed about the illicit drugs.

The White House statement did not mention whether Trump raised concern on Duterte's bloody war on illegal drugs.

The statement instead said, "They also discussed the fact that the Philippine government is fighting very hard to rid its country of drugs, a scourge that affects many countries throughout the world."

The White House said Trump "enjoyed" his conversation with Duterte as he is "looking forward to visiting the Philippines in November to participate in the East Asian Summit and the US-ASEAN Summit."

The Philippines is the ASEAN chair for 2016. Celerina Monte/DMS