Hegseth's meeting at the presidential palace in Manila comes as he opens a tour of Pacific allies that risks being overshadowed by a mounting scandal over leaked plans for military strikes.

"Deterrence is necessary around the world but specifically in this region, in your country, considering the threats from the Communist Chinese," he said.

Hegseth's Manila visit, to be followed by trips to Tokyo and World War II battleground Iwo Jima, follows months of confrontations between Philippine and Chinese vessels in the disputed South China Sea.

Beijing claims almost the entirety of the crucial waterway, despite an international ruling that its assertion has no merit.

"Friends need to stand shoulder to shoulder to deter conflict to ensure that there's free navigation, whether you call it the South China Sea or the West Philippine Sea," Hegseth said.

"Peace through strength is a very real thing", he added.

The trip, aimed at bolstering ties in the Asia-Pacific region as tensions are rising with Beijing, comes as Hegseth faces calls to resign by Democratic lawmakers and a Republican congressman's push for an independent report.

The US defence chief revealed details of strikes on Iran-backed Huthi rebels in Yemen in a group of top administration officials on the messaging platform Signal, according to a senior journalist added to the chat by accident.

On Wednesday, Hegseth mocked Atlantic magazine editor Jeffrey Goldberg's initial description of the texts as "war plans", saying they included no names, targets or classified information.

"We will continue to do our job, while the media does what it does best: peddle hoaxes," he said on social media platform X.

Hegseth is expected to meet his Philippine counterpart Gilberto Teodoro later Friday.

- Deepening cooperation -

In response to China's growing influence, the United States has been strengthening alliances with countries in the Asia-Pacific region, including the Philippines.

Manila and Washington have deepened their defence cooperation since President Ferdinand Marcos took office in 2022 and began pushing back on Beijing's sweeping South China Sea claims.

In recent years, top US officials have warned that an "armed attack" against the Philippines in the waterway would invoke the two countries' mutual defence treaty.

The two countries have expanded the sharing of military intelligence and boosted to nine the number of bases US troops have access to on the archipelago.

Given the Philippines' proximity to Taiwan and its surrounding waters, Manila's cooperation would be crucial in the event of a conflict with China.

Hegseth's visit overlaps with bilateral military exercises that will expand next month to include the countries' navies and air forces.

- 'Witch hunt' -

Despite mounting pressure over the Signal leak, US President Donald Trump has defended Hegseth.

"Hegseth is doing a great job, he had nothing to do with this," Trump said when asked by AFP whether the defence secretary should be considering his position.

"How do you bring Hegseth into this? Look, look it's all a witch hunt," Trump added in the Oval Office.

He also repeated his insistence that no classified information was shared in the breach, adding that National Security Advisor Mike Waltz "took responsibility" for the error.

Waltz added Goldberg to the group chat that included Hegseth, Vice President JD Vance, National Intelligence director Tulsi Gabbard and others.

Apart from the timing of the strikes in Yemen, Hegseth also identified the type of aircraft, missiles and drones used, according to the Atlantic, which later released screen grabs of the chat.

Democratic Senator Tammy Duckworth has said Trump should sack all the officials in the chat and called Hegseth a "liar" who "could've gotten our pilots killed".

But the White House and its allies have largely held firm in their messaging, praising the success of the attacks and slamming Goldberg as an "anti-Trump hater".

Only Secretary of State Marco Rubio has conceded there was a "big mistake".