Foreign Secretary William Hague and counterparts from 10 other nations have agreed to "provide urgently all the necessary material and equipment" to rebels opposed to Syrian president Bashar Assad.
In a communique issued after talks in Qatar the ministers demanded the withdrawal of Hezbollah militias and fighters from Iran and Iraq who had sided with Assad's regime.
Qatar's PM Sheikh Hamad bin Jassim bin Jaber al-Thani said "providing arms may be the only means of achieving peace".
Qatar's PM said arms may be the only way of securing peace
All military support will be channeled through the Syrian Supreme Military Council, the foreign ministers agreed.
The communique issued following the Doha talks also called for fighters supporting Assad to be prevented from crossing into Syria from neighbouring counties.
The ministers also pledged to pursue "all appropriate avenues" at the United Nations to "support and protect the Syrian people".
The Foreign Secretary said: "There's been a very strong common sense of purpose among the eleven countries gathered here today, all desperately concerned about foreign intervention in Syria by Iran and by Hezbollah and by the seriousness of the humanitarian situation.
"I think the main things in common and agreed are that we're all concerned about that humanitarian situation.
"The United Kingdom ... is helping to lead the way with another £175 million contribution to the humanitarian situation."
Mr Hague said: "We have been talking about how we can help the opposition, how we can help save lives. Different countries will have different ways of doing that and I've made clear before how the United Kingdom is approaching that at the moment.
"We have to cooperate and we have to coordinate as much as possible to try to save the lives of innocent people in Syria."
Syrian children waking up inside their tent in Lebanon's Bekaa Valley.
He echoed the words of US Secretary of State John Kerry at the meeting that "we're all aiming to achieve a political solution, a political settlement, in Syria but that political settlement will not come about if the opposition can be destroyed by force".
Earlier this week, the US announced it would provide Syrian rebels with "direct military aid" and Kerry reiterated that the Syrian government use of chemical weapons meant they had crossed a line.
The US Secretary of State said that providing the rebels with weapons was not to encourage "a military solution" but to enable the rebels to negotiate.
Ministers from Qatar, Saudi Arabia, the United Arab Emirates, Jordan, Egypt, Turkey, Germany, France, and Italy also attended the summit.
The ministers repeated their call for the establishment of a transitional governing body to which full executive powers would be transferred, which excluded "the central figures and associates whose hands are stained with blood".
The communique said: "In this context, Bashar Assad has no role in the transitional governing body or thereafter."
The document also called for UN inspectors to be granted full access to Syria to conduct an investigation into reported use of chemical weapons by Assad's forces.
The Doha talks came as Syrian government forces stepped up their attack against rebel strongholds north of the capital Damascus today, while opposition fighters launched their own offensive in the country's largest city Aleppo.