Britain is planning to join forces with the United States and launch military action against Syria in response to the chemical attack believed to have been carried out by President Bashar Al-Assad’s forces, the British Telegraph reported on Sunday.

Royal Navy vessels are being readied to take part in a possible series of cruise missile strikes, alongside the United States, as military commanders finalize a list of potential targets, the report said.

Government sources said talks between Prime Minister David Cameron and international leaders, including U.S. President Barack Obama, would continue, but that any military action that was agreed could begin within the next week.

The escalation comes as a direct response to what the British Government is convinced was a gas attack perpetrated by Syrian forces on a civilian district of Damascus last Wednesday.

The Assad regime has been under mounting pressure to allow United Nations inspectors on to the site to establish who was to blame for the atrocity. One international agency said it had counted at least 355 people dead and 3,600 injured following the attack, while reports suggested the true death toll could be as high as 1,300.

According to the Telegraph, Cameron interrupted his holiday for talks with Obama, French President Francois Hollande and German chancellor Angela Merkel. After discussions over the weekend, all the leaders agreed on the need for a “serious response”, according to the report.

Government sources confirmed to the Telegraph that military action was among the options “on the table” but said no decisions had been taken.

The Prime Minister, however, is believed to have abandoned hope of securing any further meaningful response from the UN amid opposition from Russia, which has already vetoed several Security Council resolutions condemning the Assad regime, including one from last week after the chemical attack.

The Royal Navy declined to comment on the current positions of its submarines, but said they regularly pass through the area on their way to the Suez Canal.

Pressure has been piling up on the West, particularly on Obama, to respond to the attack. Obama said last year that the use of chemical weapons in Syria would cross a “red line” and force a tough U.S. response, but so far has failed to deliver such a response other than deciding to directly arm selected Syrian rebel groups without publicly specifying the extent of the support.