Donald Trump's administration is edging closer to a co-ordinated military response to President Bashar Al Assad's alleged use of chemical weapons in Syria.
The US president and his defence secretary James Mattis cancelled travel plans and increased consultations both internally and with allies on Tuesday. The move followed Russia's rejection of a US draft resolution at the United Nations that sought to create a new expert group that would determine responsibility for the attacks. The Security Council voted 12-2 as Russia used its veto for the 12th time to protect its ally president Al Assad. China abstained while Bolivia voted against the resolution.
In response to the allegations, Syria said it had invited the Organization for the Prohibition of Chemical Weapons (OPCW) to investigate the suspected poison gas attack, which opposition activists say killed 40 people and wounded hundreds over the weekend.
However, a US official told The National, that while "Washington welcomes the OPCW mission, it will not affect the US decision on a response to Syria".
The move is being overseen by Mr Trump himself, who has cancelled his trip to Lima for the summit of the Americas.
Mr Trump "will not attend the 8th Summit of the Americas in Lima, Peru or travel to Bogota, Colombia as originally scheduled", the White House said. Instead he will "remain in the United States to oversee the American response to Syria and to monitor developments around the world" while dispatching Vice President Mike Pence to the meeting.
Mr Mattis also cancelled weekend travel plans to Nevada and San Francisco, in an indication that military planning could be under way and that the Syria response is being prioritised by the administration.
The US is also working to build a larger coalition. Mr Trump called UK Prime Minister Theresa May and French President Emmanuel Macron for a second time in 48 hours. US officials told Reuters that Washington is weighing a military response with London and Paris.
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Saudi Crown Prince Mohammed bin Salman announced from Paris his "readiness to work with allies on any military response in Syria if needed".
The Saudi foreign minister Adel Al Jubeir said: "There are consultations among a number of countries with regards to what steps to take in order to deal with this issue.
"Our position is that those responsible have to be held accountable and brought to justice."
The Emir of Qatar Tamim bin Hamad said ahead of his meeting with Mr Trump in the Oval Office that they see "eye to eye" on Syria and that the suffering must "stop immediately".
"We cannot tolerate a war criminal," he said, before accusing Mr Al Assad of killing half a million of his own people.
Tobias Schneider, a Syria expert at the Global Public Policy Institute in Berlin, told The National that "all signs point towards imminent US-led military action" in Syria.
"But as Barack Obama in 2013 showed us, we never really know until the moment the president gives the order," he said. Mr Trump is expected to decide his course of action by Wednesday morning local time.
Mr Schneider noted that "Russia and the Assad government are certainly working overtime to stave off the assault as Moscow ramps up its military posturing and bluster in Syria."
US officials told NBC that the Russian military has been jamming some US military drones operating over Syria, affecting American military operations.
Asked about the possible size and make-up of potential strikes, Mr Schneider said it depends on Mr Trump's intent.
"A small punitive strike like last year – basically a military slap on the wrist – would most likely hit military targets directly affiliated with the Syrian chemical weapons programme: factories, warehouses or airfields."
However, he said "a more severe response would aim to degrade the Assad regime’s ability to wage war – especially from the air by targeting a wider range of military installations and command posts, such as munitions factories and repair shops, command centres and intelligence facilities".
The US is not aiming for a “regime change” in Syria, the expert sad. “Most likely, it will look like something between last year’s tomahawk salvo and the more sustained three-day assault of Operation Desert Fox in 1998.”
As for the members of the coalition, France and Great Britain have long maintained a comparatively hard-line position towards Mr Al Assad and are likely to support the US efforts. But "it would be far more significant if any Arab states, meaning first and foremost Saudi Arabia, were to join in," said Mr Schneider.