The Philippines said Wednesday it had "vigorously" lobbied Southeast Asian nations to take a united stance critical of Beijing's claims to most of the South China Sea, but insisted a diluted statement remained a victory.

After initially denying doing so, Foreign Secretary Perfecto Yasay said he lobbied his counterparts at a meeting of the 10-member Association of Southeast Asian Nations (ASEAN) in Laos this week to refer to the verdict in a statement issued on Monday.

The statement avoided mentioning this month's ruling by a UN-backed tribunal in The Hague that Beijing's claims to almost all of the strategic waterway had no legal basis, instead calling merely for "self-restraint".

Asked at a news conference in Manila if he pushed for ASEAN to refer to the ruling, Yasay said: "Yes, vigorously".

However he said the statement was a "victory" for ASEAN, as it referred to upholding principles of international law.

The Philippines, under the previous administration of Benigno Aquino, launched the legal challenge in 2013 against China's claims to most of the sea.

China insists it has sovereign rights to nearly all of the sea, including waters approaching ASEAN members the Philippines, Vietnam, Malaysia and Brunei.

Efforts to forge a united ASEAN front on the issue have crumbled in recent years as China has successfully lobbied Cambodia and Laos, which are members of the bloc but Chinese allies.

The Philippines has also adopted a more moderate stance on China under the new government of President Rodrigo Duterte, who has courted closer Chinese economic and political ties since taking office on June 30.

Yasay initially said on Tuesday he had not asked ASEAN members to refer to the ruling in its end-of-meeting statement.

"No. Never, never did. Please don't put words into my mouth," Yasay told reporters in Vientiane when asked if he had called for a reference.

"The other countries are not part of our filing of the case before the arbitral tribunal so why would we insist that it be put in the ASEAN statement?"

Back in Manila on Wednesday, Yasay denied making those comments.

"I never said those things, all right? And please don't put words into my mouth," he told reporters.

A recording of Tuesday's interview in Vientiane by an AFP reporter confirmed Yasay's initial comments.

When asked to explain why Yasay denied lobbying, a foreign affairs spokesman said Wednesday he was unable to clarify.

Diplomats attending the meeting also told AFP that Yasay had pushed for a reference to the tribunal's verdict.

Adding to the confusion, Cambodia's foreign ministry spokesman Chum Sounry said his nation had not vetoed Philippine efforts.

He said Yasay withdrew his request for the tribunal mention, after discussions in which Cambodia made clear it wanted to remain "neutral".

"The Filipino foreign minister himself decided to remove (it) and not to mention the ruling," Chum Sounry said.