US President Barack Obama has delayed cruise missile strikes by five destroyers already off the coast of Syria in order to seek approval from Congress. Three destroyers generally patrol the region.
The Nimitz had been in the Indian Ocean and was due to sail east around Asia to Washington, Reuters said.
The Navy has also sent the USS San Antonio to join the five destroyers, diverting it from a voyage further to the west. The amphibious ship has 300 Marines and has been asked to serve as a forward staging base, which could provide a temporary base for special operations forces, Reuters said.
The delay in military action for at least a week has meant that in Britain, Prime Minister David Cameron is under increasing pressure to return to Parliament for another vote on British involvement.
Lord Michael Howard, a former Conservative leader, Sir Malcolm Rifkind, a former Foreign Secretary, and Lord Paddy Ashdown, a former Liberal Democrat leader, led calls to vote again.
Rifkind, the chairman of the intelligence and security committee, said the situation has "moved on dramatically now" and that the evidence is "becoming more compelling every day".
Boris Johnson, the London Mayor, has also suggested another motion could be put "inviting British participation". Johnson, who has been highly sceptical of intervening in Syria, believes that Parliament has helped the international community by allowing a delay in the action for further evidence to be collected.
Signs of Labour disagreements over Opposition Leader Ed Miliband's response to the Syrian crisis were also beginning to emerge.
Jim Murphy, the shadow defence secretary, became the first senior Labour figure to admit that the case against the Assad regime over last month's chemical weapons attack was not in doubt.
Ben Bradshaw, a former Labour Cabinet minister, suggested he would now support a second parliamentary vote being called.
Chancellor of the Exchequer George Osborne and Foreign Secretary William Hague, Cameron's two most senior Cabinet colleagues, appeared to rule out a second vote on Syrian action.
However, Hague laid out a series of conditions which would have to be met before action could be reconsidered - primarily involving Miliband offering to co-operate. He also warned that if Bashar al-Assad is not confronted now it would lead ultimately to a "confrontation [which] will only be bigger and more painful".
Since last Friday, when British MPs rejected government backing for potential military action against Syria by just 13 votes, the US Administration has released detailed intelligence on Assad's alleged involvement in a chemical weapons attack on a suburb of Damascus. A report from UN weapons inspectors is also imminent and yesterday a new intelligence report from France suggested that Assad had amassed 1000 tonnes of chemical weapons.
John Kerry, the US Secretary of State, said his Government had now concluded that sarin gas was used in the attack, which the US claims killed 1429 people, including 426 children. The Americans set out detailed intelligence on the attack, including information about where the missiles had been fired from, telephone intercepts and other evidence. This compares with an overall conclusion from British spies last week that the Syrian leader was highly likely to have been responsible.
Kerry linked Assad to Adolf Hitler and Saddam Hussein as the only leaders to breach an almost century-old taboo against chemical weapons.
He said he refused to believe the US Congress would allow the Syrian regime to get away with murder.
"I can't contemplate that the Congress would turn its back on all of that responsibility and the fact that we would have in fact granted impunity to a ruthless dictator to continue to gas his people," he said on Fox News.
The use of sarin, which Kerry said was detected in soil and blood samples obtained by the US from first responders, is significant because the nerve agent is proscribed as a weapon of mass destruction under UN resolution 687.
Kerry fought off criticism from home and abroad that Obama had made himself look weak and indecisive, telling CNN the President retained the right to use force even if he lost the vote but "believes that we are stronger as a nation when we act together".
Yesterday, a report by France's intelligence agencies said that Assad's regime had amassed more than 1000 tonnes of chemical weapons, including sarin, mustard gas and VX gas.
The study, by the Direction Generale de la Securite Exterieure, said Assad and the most influential members of his clan were the only ones able to give the order to use chemical weapons.
Sarin gas
Appearance: Odourless, tasteless, colourless.
Form: Liquid vapourises quickly into gas and spreads.
Absorption: Contact with skin, inhalation or ingestion.
Effects: Inhalation can cause death within 1-10 minutes.
History: Man-made nerve gas developed during World War II. Quickly breaks down after release but minuscule amounts can persist in victims' blood for 16-26 days.
Evidence: UN inspectors needed soil, blood or hair samples from the attack area or victims to examine.
Nerve gas action
1) The nervous system relies on the transmission of signals through nerve junctions called synapses.
2) An impulse triggers the release of a chemical neurotransmitter, acetylcholine (ACh).
3) ACh attaches to a receptor molecule, stimulating the cell to fire off impulses.
4) An enzyme breaks ACh down to free up the receptor site - preventing over-stimulation.
5) Sarin molecules block the enzyme that breaks down ACh and so increase the ACh level at the receptor.
6) The receptor fires off impulses as victim rapidly loses control of vital functions.
- Graphic News
