MANILA - The Philippines' intent to terminate its Visiting Forces Agreement (VFA) with the United States is a "serious step with significant implications" on the long-standing alliance between the two countries, the United States Embassy in Manila said Tuesday.

In its first statement since President Rodrigo Duterte ordered the treaty cancellation, the US Embassy confirmed it has been informed by the Department of Foreign Affairs of the Philippine move, and that it would see how it would respond.

"This is a serious step with significant implications for the U.S.-Philippines alliance. We will carefully consider how best to move forward to advance our shared interests," the embassy said.

Despite the Philippine action, the US said it is still committed to the friendship between the two sides.

"Our two countries enjoy a warm relationship, deeply rooted in history. We remain committed to the friendship between our two peoples," it said.

Duterte on Jan.23 said he would terminate the VFA after the US canceled the visa of his long-time ally Sen. Ronald Dela Rosa, among key enforcers of his drug war when he was police chief.

The reason for the visa cancellation was unclear, but Dela Rosa said it may be linked to his role in the anti-drug campaign, which several US officials have criticized.

On Tuesday, Malacañang said the Philippines has formally notified the US of its intent to pull out of the agreement, which governs the conduct of visiting American forces in the Philippines.

The notice, signed by Foreign Affairs Secretary Teodoro Locsin Jr., was received on the same day by US Deputy Chief of Mission John Law.

Duterte had given orders to go ahead with the termination process Monday night, Presidential spokesperson Salvador Panelo said.

• Philippines sends notice of VFA termination to US

The order came even as lawmakers called first for a review of the agreement, which is among the Philippines' defense pacts with the US.

In a Senate hearing last week, Locsin cited the many benefits the Philippines has from its defense alliance with the world superpower, including billions worth in defense equipment, training support and humanitarian assistance.

• IN NUMBERS: How beneficial is VFA to the Philippines?

The two countries' relationship is sealed by the 1951 Philippine-US Mutual Defense Treaty, which obligates both sides to come to each other's defense in case of an attack by a third party.

In 2014, the two sides signed the Enhanced Defense Cooperation Agreement, which allows greater rotational presence of US troops in the Philippines.

Since the start of his presidency, Duterte has veered away from the country's traditional ally, turning to the latter's economic and military rivals China and Russia.

He has also declined White House invitations to visit the US, himself expressing apprehensions if he would be granted a visa.

• Duterte rejects US invite for leaders’ summit