China on Tuesday warned against military action in Syria after US President Donald Trump vowed to respond "forcefully" to the latest alleged chemical atrocity in the country's bloody civil war.

As he opened a cabinet meeting at the White House on Monday, Trump pledged "major decisions" to come within the "next 24-48 hours" after what he called a "heinous attack on innocent" Syrians in the rebel-held town of Douma that killed at least 40 people.

The Syrian regime and its ally Russia have rejected claims of a chemical attack, with President Vladimir Putin warning against any "provocation and speculation on this matter".

Trump -- who last year launched a missile strike on a Syrian regime air base after another alleged chemical attack -- warned Sunday that there would be a "big price to pay".

The crisis was discussed Monday at an urgent UN Security Council meeting, while the US also circulated a draft resolution for a new independent inquiry of chemical weapons attacks in Syria.

At a regular press briefing in Beijing on Tuesday, Chinese foreign ministry spokesman Geng Shuang said his country was "opposed to the wanton use of force or threat of force".

Before a "comprehensive, impartial and objective investigation" had been conducted into the incident, no party should "prejudge the results and come to conclusions randomly," he said.

"Military means will lead us nowhere."

China depends on the Middle East for its oil supplies but has long taken a back seat in the region's disputes, only recently beginning to expand its role, hosting high-level delegations from both the Syrian government and the opposition.

It consistently says the crisis needs a "political solution" but has numerous times vetoed UN Security Council measures aimed at addressing the conflict -- including an investigation of war crimes in the country.