The United States is mulling ways to step up support for the Syrian opposition, a top US official said Wednesday, as US Secretary of State John Kerry and G8 ministers were to meet rebel leaders.

The aim was to “move to a transition government that reflects the legitimate desires of the people,” the official said.

The battle to oust Syrian President Bashar al-Assad is now in its third year, with an estimated 70,000 people said to have been killed and millions forced to flee their homes.

Kerry was to meet later with Syrian opposition prime minister Ghassan Hitto and other top coalition members on the sidelines of a G8 foreign ministers meeting in London, for talks hosted by British Foreign Secretary William Hague.

So far the United States has been the single largest donor of humanitarian aid to the Syrian people, spending $385 million through aid agencies and the United Nations for food, shelter and medical aid.

It has also provided around $115 million in non-lethal aid for such items as communications equipment, and is beginning to distribute food and medical supplies to the Free Syrian Army.

But despite plans put forward by various sections of the US government, President Barack Obama has refused to arm the opposition fearing that weapons could get into militant hands in a volatile and complex conflict.

Kerry told reporters Tuesday that the White House would make any announcements on “stepped-up efforts” for the Syrian opposition.

But he added: “I will say that those efforts have been very much front and centre in our discussions in the last week in Washington.”

The US official speaking to reporters in London refused to go into any specifics of what such stepped-up efforts might include.

But the official added that “all of the implications of making those choices” including “the legal authority… and the capacity to make the best use of material” had to be considered.

The G8 ministers would discuss the Syrian crisis at a dinner on Wednesday night, and was expected to issue “quite a strong statement” at the end of their two-day meeting.

But the official admitted there had been “some vigorous discussion” about the statement, with some objections particularly from the Russian side, which remains a key ally of the Assad regime.