"Aiding the people who are fighting for a free Syria is a cause to which President Obama and all of us are deeply committed," Kerry said Thursday during a media availability while in Rome for a "Friends of Syria" meeting.
World powers are united in their belief that the best solution for Syria is a political one, Kerry said.
"The sooner we can get started, the more lives we'll save, and the better chance we have of preserving Syria's institutions and its rich culture and of restoring its unity," he said.
"Working together, we've already been able to do a lot," Kerry said of the international effort to resolve the crisis in Syria, including sanctions against President Bashar Assad's regime, supporting the Syrian Opposition Coalition with training, organization and some communications resources, as well as humanitarian support.
Kerry announced the United States would contribute $60 million directly to rebels fighting against President Bashar Assad's regime. Among other things, he said the aid would strengthen the Syrian Opposition Coalition's organizational structure; helping war-torn communities with respect to sanitation, food delivery and medical care, and speed up delivery of basic goods and services, including security and education.
Kerry said the United States and its partners have meet regularly and all agree that "we need to change President Assad's calculation, and we need to do more."
The aid falls short of what rebels have requested -- arms.
"We do this because we need to stand on the side of those in this fight who want to see Syria rise again in unity and see a democracy and human rights and justice," he said. "The stakes are really high. And we can't risk letting this country, in the heart of the Middle East, be destroyed by vicious autocrats or hijacked by the extremists."
He expressed confidence that the money would be delivered "rapidly," noting part of it would be channeled into activities already in progress.
Kerry said he would brief Congress as soon as he returns to Washington and would "personally be engaged in that process."
The United States has provided humanitarian supplies, communications equipment and training to Syria's opposition. However, Thursday is the first time Washington said it would work directly with Syria's rebel fighters through the Supreme Military Command attached to the Syrian Opposition Coalition.
U.S. officials told The Wall Street Journal they would vet rebel factions of the Supreme Military Command to ensure the United States doesn't end up supplying radical Islamist groups or militias tied to al-Qaida.
No deadline was announced for when the aid would reach Syria's fighters.
Britain was expected to support the Supreme Military Command by agreeing to send night-vision equipment, military-support vehicles and body armor, the Journal said.
In New York, Syrian Ambassador to the United Nations Bashar Jaafari told al-Jazeera the Friends of Syria should not simply meet with Syria's opposition -- it should sit, and insist the opposition also sit, with the Assad regime for an unconditional national dialogue.
"If they are really the Friends of Syria, they should care for all the Syrian people, not only part of the Syrian people, those who are refusing categorically to sit at the table of the national dialogue and calling for further destruction of the Syrian state," Jaafari said.