United States President Barack Obama has the authority to launch air strikes against Syria. But he has to notify legislators in Congress - a process which Secretary of State John Kerry says has begun.
"The Administration is actively consulting with members of Congress, and we will continue to have these conversations in the days ahead," Kerry said yesterday.
However, a spokesman for the Republican speaker of the House Of Representatives John Boehner said those conversations had not yet begun.
In 1973, after the Vietnam War and despite the opposition of Richard Nixon in the White House, Congress passed the War Powers Resolution to compel Presidents to seek congressional approval in order to deploy soldiers.
A President must, in theory at least, obtain an authorisation voted on by Congress if introducing troops into "hostilities" or "situations where imminent involvement in hostilities is clearly indicated by the circumstances" to keep the operation going beyond 60 days.
In practice, all Presidents since Nixon have deemed this unconstitutional and regularly neglected to ask for such permission, instead simply notifying Congress.
Obama, leaning on a United Nations Security Council resolution, launched aerial strikes against Muammar Gaddafi's troops in Libya in March 2011. But according to the Administration, the operation did not fall within the "hostilities" outlined in the 1973 law.
In the wake of the strikes, Congress was split between backers of a law mandating the President stop the intervention and those who wanted to formally authorise it.
In March 1999, legislators also didn't have a say on the long bombing campaign in Kosovo, launched by then-President Bill Clinton.
"They do not need an authorisation but I hope they will come for one," Bob Corker, the top Republican on the Senate Foreign Relations Committee, told broadcaster MSNBC of a possible Syria strike.
"They can start but hopefully as soon as we get back [from recess], Congress will take up an authorisation for this," he added. According to the senator, a response on Syria is imminent and US military assets are in place.
For now, the calendar is on Obama's side since Congress is on summer recess until September 9.
In Britain, Prime Minister David Cameron is facing demands to set out the legal justification for military action against Syria amid mounting unease over the scale and speed of Britain's commitment to another conflict in the Middle East.
Britain, America and France are united in their readiness to act and do not require any further United Nations resolution under international law, said Foreign Secretary William Hague.
The Russian Government has warned that a strike without UN backing would be a "blatant violation of international law" that would worsen the situation on the ground.
Cameron telephoned President Vladimir Putin and told him there was little doubt that the Assad regime was responsible for the Damascus attack. The Russian President refused to accept that there was enough evidence of a chemical attack or that forces loyal to the regime were responsible.
In America, Kerry said the evidence was "undeniable" despite attempts by the Assad regime to "systemically destroy" it. He said the US had additional information which would be reviewed with allies before any military response.
Cameron and Nick Clegg, his Liberal Democrat deputy, will decide today whether MPs should be recalled this week amid demands by MPs from all sides for a debate and a binding "vote" before any action. Labour formally demanded that ministers make their case to Parliament first.
Hague said that Britain faced a choice between military strikes or allowing tyrants to use chemical weapons with impunity. He said that efforts at the UN had failed and it would be legal for countries to take military action in response to chemical attacks without Security Council backing.