The government of Philippine President Rodrigo Duterte announced Tuesday it had suspended plans to cancel the Visiting Forces Agreement (VFA), a deal that is important to Washington's moves to counter Beijing's rising regional power.

Duterte has cosied up to China in search of trade and investment, sparking US concern that its long-time ally and former colony would change sides in a strategic boost to Beijing.

"Because of security issues... in that part of the world (South China Sea), both our governments have seen it would be prudent for us to simply suspend any implementation of the termination," Philippine Ambassador to the US Jose Manuel Romualdez told ANC news channel.

Since taking power in 2016 Duterte has moved closer to Beijing, but has faced push back from the Philippine public and concern in the military wary of its territorial ambitions in the disputed South China Sea.

Billions in trade pass through the strategic waterway and it is thought to contain rich petroleum deposits, making it a frequent source of regional tension.

Philippine analyst Richard Heydarian said the VFA reversal showed Duterte had to decide between an aggressive China and an historic ally that has been helpful.

"This is not the time to initiate an ugly divorce, especially when China is spreading its tentacles everywhere," he said.

The 1998 pact is key to the US-Philippines' broader decades-old military alliance, and underpins hundreds of joint military activities per year as well as speedy disaster aid and ongoing anti-terror efforts.

The Philippine military receives significant American training and equipment, obtaining $554.55 million in US security assistance from 2016-2019.

Manila's termination of the military pact was to have taken effect in August and was triggered by the cancellation of the visa of Ronald Dela Rosa, a senator who served as the main architect of Duterte's drug war.

Duterte bristles at any criticism and sanction of his signature policy, which has seen police kill thousands of alleged drug users and pushers.

Though Duterte has repeatedly threatened to pull the Philippines away from the US, ties have remained close.

Romualdez said a US offer to assist the Philippines in its battle to contain its coronavirus outbreak also helped discussions on preserving the VFA for now.

The suspension is for six months from June 1 and can be extended a further six months.

An extension of the reversal would push the deal's life up to the final year of Duterte's constitutionally-mandated single term, which ends in June 2022.