ISTANBUL — The United States and dozens of other countries moved closer on Sunday to direct intervention in the fighting in Syria, with Arab nations pledging $100 million to pay opposition fighters and the Obama administration agreeing to send communications equipment to help rebels organize and evade Syria's military, according to participants gathered here.

The moves reflected a growing consensus, at least among the officials who met here this weekend under the rubric "Friends of Syria," that mediation efforts by the U.N. peace envoy, Kofi Annan, were failing to halt the violence in Syria and that more forceful action was needed.

With Russia and China blocking measures that could open the way for military action by the United Nations, the countries lined up against the government of President Bashar Assad have sought to bolster Syria's beleaguered opposition through means that seemed to stretch the definition of humanitarian assistance and blur the line between lethal and nonlethal support.

There remains no agreement on arming the rebels, as countries like Saudi Arabia and some members of Congress have called for, largely because of the uncertainty regarding who exactly would receive the arms.

Still, the offer to provide salaries and communications equipment to rebel fighters known as the Free Syrian Army — with the hopes that the money might encourage government soldiers to defect, officials said — is bringing the loose Friends of Syria coalition to the edge of a proxy war against Assad's government and its international supporters, principally Iran and Russia.

Direct assistance to the rebel fighters, even as Assad's loyalists press on with a brutal crackdown, risked worsening a conflict that has already led to about 9,000 deaths and could plunge Syria into a protracted civil war. Some say that enabling the uprising to succeed is now the best bet to end the instability and carnage sooner.

"We would like to see a stronger Free Syrian Army," Burhan Ghalioun, the leader of the Syrian National Council, a loose affiliation of exiled opposition leaders, told hundreds of world leaders and other officials gathered here. "All of these responsibilities should be borne by the international community."

Ghalioun did not directly address the financial assistance from the Arab countries — including Saudi Arabia, Qatar and the United Arab Emirates — but he added, "This is high noon for action."