The core group of the "Friends of Syria" will meet next week in Istanbul and US Secretary of State John Kerry will attend, a senior US State Department official said Wednesday.
"The secretary will be attending the next core group meeting in Istanbul on Saturday the 20th," the official said, asking not to be identified.
But the official, speaking in London where Kerry is meeting G8 foreign ministers, did not immediately give further details.
The "Friends of Syria", comprising the United States, European and Arab countries opposed to the rule of President Bashar al-Assad, held their last major meeting in Rome in February.
Syrian opposition leaders met with Kerry on the sidelines of the G8 talks where they renewed appeals to be supplied with arms without going into specifics, although Kerry "didn't promise anything," a second State Department official said, also asking not to be identified.
So far the United States has refused to arm the rebels, fearing the weapons could fall into the wrong hands.
"We are always considering a variety of options. We are going to continue to aid the opposition, working with them in terms of what they need, in terms of what we're willing to provide," the official said.
Wednesday's talks had focused on ways of changing Assad's calculations about the outcome of the conflict which is now in its third year and has cost some 70,000 lives, according to the UN.
"Kerry talked about ways that we can make sure that we change President Assad's calculation. He talked about the need for us and the core group to figure out ways that we can be more effectively aiding the opposition," the US official said.
"We need to have this continuing conversation which is why we are going back to Istanbul, so we can push things forward".
But he said the lunch with six Syrian opposition leaders including new prime minister Ghassan Hitto and hosted by British Foreign Secretary William Hague was "a good, substantive discussion".
All sides emphasised "the importance of working together, the importance of them getting themselves more organised, which they said they were in the process of doing".
Earlier another American official said Washington was mulling ways to step up support for the Syrian opposition.
"The United States every single day thinks about what more we can do to help bring this horrible situation to an end," the official said, asking not to be identified.