Direct British military involvement in Syria will not be authorised in Thursday's House of Commons vote, after Labour threatened to oppose the Government's motion.
Any direct action by UK forces will require a further vote in the Commons once the United Nations has considered a report from weapons inspectors investigating the alleged use of chemical weapons in Damascus.
But the motion will ask MPs to agree the principle that a "strong humanitarian response" is required from the international community and "this may, if necessary, require military action that is legal, proportionate and focused on saving lives by preventing and deterring further use of Syria's chemical weapons".
Chief Political Correspondent Jon Craig said: "This motion looks very bland, very uncontroversial.
"(Prime Minister David Cameron) has put off a decision really and that will be seen as a climbdown."
Labour had said it would oppose the Government's motion on Syria unless it insisted on waiting for UN inspectors' report.
It tabled an amendment outlining conditions it said should be met before any intervention to deter the further use of chemical weapons, after last week's attack that allegedly killed more than 1,300.
It demanded "compelling evidence that the Syrian regime was responsible for the use of these weapons", that action would be legal in international law and that the Parliament can vote on UK participation.
A Labour source said: "We cannot give the PM a blank cheque. We should see the UN evidence before making a decision. This conflict has been going on for two and a half years. If it takes another two and a half days we will do so."
In New York, Russian Foreign Minister Sergei Lavrov also told the British Government that the United Nations Security Council should not consider a draft resolution before inspectors reported their findings there, saying it was necessary "to wait for the results"
US President Barack Obama said he had not made a decision on Syria and that American engagement in a civil war in the country would not help.
But he said the US had "concluded" that the Syrian government had carried out the chemical attack, while a State Department spokeswoman said the US would respond even in the absence of UN backing.
Marie Harf said: "We cannot be held up in responding by Russia's intransigence - continued intransigence - at the United Nations. The situation is so serious that it demands a response."
Earlier Foreign Secretary William Hague had said the UK may act whether or not a consensus was reached by the five permanent members of the United Nations Security Council.
"We believe that it's time the United Nations Security Council shouldered its responsibilities on Syria, which for the last two and a half years it has failed to do," he said.
"We have to confront something that is a crime against humanity. If we don't do so we will have to confront even bigger war crimes in the future."
Mr Hague said "all the evidence" pointed to Bashar al Assad's regime being behind the chemical weapon attack.
But he later said the motion eventually put forward "reflects the deep concerns in this country about what happened in Iraq" and stressed the Government's desire for a "consensual" approach.
Syria's deputy foreign minister claimed Britain, the US and France helped "terrorists" use chemical weapons in Damascus.
"The terrorist groups are the ones who used them with American, British and French encouragement. This encouragement should stop," said Faisal Al-Miqdad.
But the US is reportedly certain the poison gas attack in Syria was carried out by the Assad-regime after listening to intercepted telephone calls .
Intelligence officers allegedly overheard panicked conversations in which a Syrian defence official demanded an explanation for the attack from a leader of a chemical weapons unit.
UN Secretary-General Ban Ki-moon had urged all sides to prioritise a diplomatic solution and said his team needs until Sunday to establish the full facts of the alleged chemical attack.
UN weapons inspectors visited at the site of the alleged attacks again on Wednesday morning, a day after suspending their mission over safety concerns.
The inspectors came under sniper fire when they began their operation on Monday.
This afternoon's NSC meeting discussed intelligence gathered by UN inspectors from their initial visit to Mouadamiya.
General Sir Nick Houghton, chief of the defence staff, was also expected to outline a series of options for targeted attacks.
It is understood the most likely military response would be a strike launched from US Navy warships, several of which have been repositioned in the eastern Mediterranean, against targets such as command and control bunkers.
But defence analyst Francis Tusa told Sky News: "I'm not necessarily sure it puts any particular pressure on the regime to change its behaviour. Losing the odd bit of hardware that the Russians will replace for free doesn't seem to be that much of value."
Iran's Supreme Leader, Ayatollah Ali Khamenei, responded to the rising tensions, reportedly saying that US military intervention would be "a disaster for the region".
"The region is like a gunpowder store and the future cannot be predicted," Iran's ISNA agency quoted him as saying.
Turkey and Iraq both say they have placed their military on high alert.
Nato has given its support for tough action against Syria, "condemning in the strongest possible terms these outrageous attacks" and saying "those responsible must be held accountable".
But hundreds of protesters, carrying banners and chanting slogans such as "Hands off Syria" and "Cut War Not Welfare", gathered outside Downing Street to oppose any Western intervention in Syria.
While political momentum towards intervention mounts, the British public has yet to be persuaded.
A YouGov survey for The Sun revealed that nearly three-quarters of people oppose the deployment of British troops to Syria.
And a majority of 3-1 believe the Government should be bound by Parliament's vote.