Western countries have so far shied away from arming the rebels fighting against President Bashar al Assad, despite giving diplomatic backing to efforts to remove him.
The rebels have been receiving increasingly large shipments of arms through Turkey and Jordan in recent months, with funding for them believed to come from wealthy Arab states.
Washington said it would provide non-lethal aid to Syrian rebels to bolster their popular support. The package is likely to include medical supplies, food and $60 million. New US Defence Secretary Chuck Hagel said last Friday giving only non-lethal support was correct.
Britain has in the past offered non-lethal aid such as radios, body armour and medical supplies to the rebels. Mr Hague will make an announcement to parliament this week about more aid, but told BBC yesterday it would not include weapons.
But he said: "I don't rule out anything for the future. If this is going to go on for months or years ... and countries like Iraq and Lebanon and Jordan are going to be destabilised, it's not something we can ignore.
"You can reach the point eventually where humanitarian need is so great and the loss of life so great that you have to do something new in order to save lives."
Mr Hague has previously said Britain was keeping its options open in Syria, and the Foreign Office said his remarks did not signal a shift in policy.
Nevertheless, the question of whether the West will shift to explicit military support is being closely watched as Syrian opposition leaders are trying to demonstrate that they can curb the influence of Islamist radicals, whose presence deters the West from helping.
In a televised interview broadcast on Saturday, Mr Assad said Britain's involvement in the Syria crisis was naive and unrealistic.
"How can we expect them to make the violence less when they want to send military supplies to the terrorists?" he said.
Mr Hague dismissed Mr Assad's remarks as delusional, saying: "This is a man presiding over this slaughter. The message to him is: 'We, Britain, are the people sending food and shelter and blankets to help people driven from their homes and families in his name'."
Iran, Mr Assad's main ally, also criticised the West for pledging more aid to fighters.
"The announcement of more help for terrorists by political authorities is a big mistake and they will soon see the results," said Revolutionary Guards commander Brigadier-General Massoud Jazayeri.
"Some European countries and America who are causing the chaos in Syria will be targeted heavily by these same terrorists - this is a precursor to transferring the agitation from Syria to other places," he said.
Two years of war in Syria has killed 70,000 people and driven millions from their homes. The opposition controls substantial territory, but is outgunned by Mr Assad's forces.
Mr Hague said he would seek a diplomatic breakthrough during talks with his Russian counterpart this week, but had little hope for now. Moscow has backed Mr Assad and says his exit from power should not be a pre-condition for a negotiated settlement.
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