Discussions between ministers and officials on military, humanitarian and diplomatic options for halting the bloodshed and refugee crisis were chaired by Prime Minister David Cameron.
He last week ordered all options, including arming rebel forces opposed to president Bashar Assad, to be put back on the table amid frustration at international failure to curb the bloodshed.
The NSC meeting came a day before opposition leaders, who agreed the formation of a coalition at the weekend in an effort to unite disparate factions fighting Assad, are due in London for talks.
The US and the UK have signalled support for the grouping but stopped short of the formal recognition of it as a government-in-waiting already accorded by France.
Mr Hague declined to give details of what was discussed at the NSC but indicated that he would make a statement to MPs when the Commons returns next week.
Among other measures thought to be under consideration is the creation of UN-protected “safe zones” within Syria’s borders to protect civilians.
“I will be meeting tomorrow some of the figures, some of the leaders of the new opposition coalition, and we will want to discuss with them their way forward, the need for them of course to win over the middle ground of opinion in Syria, to work effectively together, to be inclusive, to respect human rights and to have a clear plan for political transition in Syria.
“Our work with the opposition is a high priority,” Mr Hague said.
Downing Street said the hour-long NSC meeting involved “a thorough discussion of the full range of options” – military as well as political and diplomatic.
Among those involved was head of the Armed Forces Sir David Richards who has warned that cuts to the services mean they cannot do everything ministers would like.
The meeting reached agreement on the need to “intensify discussions with partners” in an effort to secure tougher co-ordinated action, No 10 said.
Among controversial strategies being considered by Mr Cameron is allowing Assad a safe passage out of Syria even if that means he evades international justice.
Officials are also examining the terms of the EU embargo which prevents the UK directly supplying the rebels with arms for ways to justify such a move.
Diplomatic talks with commanders on the ground – though held outside Syria – have already been sanctioned by Mr Hague to be led by his special envoy, Jon Wilks.