Russia and the United States have tangled at the UN Security Council over Syria as they blocked attempts by each other to set up international investigations into chemical weapons attacks in the war-ravaged country.

The United States and other Western powers are considering taking military action over a suspected poison gas attack on Saturday on a rebel-held Syrian town that long had held out against President Bashar al-Assad's forces.

Russia vetoed a US-drafted resolution to create a new inquiry to ascertain blame for such attacks.

The US and other countries then blocked a rival Russian bid to set up a different probe that would require the Security Council to attribute responsibility.

Russia opposes any Western strike on its close ally Syria.

A Russian-drafted resolution expressing support for sending investigators from the global chemical weapons watchdog agency to the site of the alleged deadly attack also failed to pass.

The Organisation for the Prohibition of Chemical Weapons said earlier that inspectors would travel to the Syrian rebel-held town of Douma to investigate reports of the attack that killed as many as 60 people.

Russian UN Ambassador Vassily Nebenzia said the US decision to put forward its resolution could be a prelude to a Western strike on Syria.

"The United States is again trying to mislead the international community and is making yet one more step toward confrontation," Mr Nebenzia told the 15-member Security Council.

"It is clear that the provocation step has nothing to do with a desire to investigate what happened."

More than 1,000 people were injured in Saturday's suspected chemical weapons attack on Douma, according to a Syrian relief group.

Doctors and witnesses have said victims showed symptoms of poisoning, possibly by a nerve agent, and reported the smell of chlorine gas.

US Ambassador to the United Nations Nikki Haley told the Security Council that adopting the US-drafted resolution was the least that member nations could do.

"History will record that, on this day, Russia chose protecting a monster over the lives of the Syrian people," Ms Haley said, referring to Mr Assad.

Twelve council members voted in favour of the US-drafted resolution, while Bolivia joined Russia in voting no, and China abstained.

A resolution needs nine votes in favour and no vetoes by Russia, China, France, Britain or the United States to pass.

US President Donald Trump cancelled a planned trip to Latin America later this week to focus on responding to the Syria incident, the White House said.

Yesterday, Mr Trump warned of a quick, forceful response once responsibility for the attack was established.

International chemical weapons experts will go Douma to investigate the suspected poison gas attack, their organisation has said.

British Foreign Secretary Boris Johnson has said Russia was holding the Syrian people to ransom by failing to back the resolution.

"Hugely disappointing that Russia vetoed the proposal at the UN for an independent investigation into Syrian chemical attacks," Mr Johnson said on Twitter.