Western and Arab nations have called on UN-Arab League special envoy Kofi Annan to determine a timeline of steps needed to persuade President Bashar al-Assad to end the conflict in Syria.
The "Friends of Syria" said in a final communique on Sunday that Assad did not have an open-ended opportunity to meet his commitments to Annan.
"The regime will be judged by its deeds rather than its promises," the group of 83 nations said after the one-day meeting in Istanbul .
Al Jazeera's Anita McNaught, reporting from Istanbul, said the meeting was marked by a "remarkable change of tone".
"[US Secretary of State] Hillary Clinton made a very strong statement and intriguing promises. The key phrase from her was that there is no more time for excuses or delays. Today's meeting was a moment of truth," McNaught said.
Assad has accepted, but not yet implemented, Annan's six-point plan, which calls for the military and armed opposition to cease fire, withdraw from towns and cities, and allow humanitarian access.
"We will not let the Syrian regime misuse another opportunity, which is the last chance for the situation in Syria," Ahmet Davutoglu, the Turkish foreign minister, told a news conference after the meeting.
The "Friends of Syria" recognised the opposition Syrian National Council (SNC) as a legitimate representative of all Syrians, and "noted" it as the main opposition interlocutor with the international community, wording that stopped short of full recognition of a group hampered by disunity.
The group made no mention of supporting or arming the opposition Free Syrian Army [FSA], as advocated by some Gulf Arab states, but said it would "continue to work on additional appropriate measures with a view to the protection of the Syrian people".
'Pot of gold'
The international coalition also said it will provide funding and communications equipment to Syrian rebels and opposition activists, reflecting a shift toward military options that might oust Assad after a year of failed diplomacy aimed at stopping his crackdown on dissent.
"Do not prolong the catastrophe," said Syrian National Council member Burhan Ghalioun
Participants at the meeting said Saudi Arabia and other Gulf countries are creating a multi-million-dollar fund to pay members of the FSA and soldiers who defect from the regime and join opposition ranks.
One delegate described the fund as a "pot of gold" to undermine Assad's army.
The large-scale plan by Gulf countries to help Syria's badly over-matched rebels offers a solution to the international divide over whether to arm the rebels or support them through only non-lethal or humanitarian means.
It also reflects frustration with appeals to Assad to stop his crackdown on dissent, as well as hopes of forcing his removal by shifting the military balance on the ground.
Meanwhile, Iraq has said Arab nations should not arm or financially assist Syrian rebels. It said doing so would only make the conflict worse.
Speaking in Bagdad, Iraqi Prime Minister Nuri Al-Maliki said: "We reject any arming of the opposition, we reject attempts to bring down the regime by force, because it will leave a wider crisis in the region."
China and Russia absent
The Saudis and other Arab Gulf states have proposed giving weapons to the rebels, while the US and other allies, including Turkey, have balked out of fear of fueling an all-out civil war. Washington hasn't taken any public position on the fund, but it appears that it has given tacit support to its Arab allies.
The salaries would aim to entice reluctant servicemen in Assad's military to break ranks and join the insurgency. With Syria's economy in a spiral, the Syrian opposition and US and Arab officials hope soldiers will desert in large numbers and accelerate the downfall of the Assad regime.
Delegates from dozens of countries also sought to increase pressure on Assad by pushing for tighter sanctions and increased diplomatic pressure, while urging the opposition to offer a democratic alternative to his regime.
The show of solidarity at the "Friends of the Syrian People"conference was marred by the absence of China, Russia and Iran, key supporters of Assad who disagree with Western and Arab allies over how to stop the bloodshed.
Clinton expressed skepticism that the Syrian government would observe Annan's plans, which call for an immediate cease-fire and a Syrian-led negotiation process.
"Nearly a week has gone by, and we have to conclude that the regime is adding to its long list of broken promises," Clinton said. "The world must judge Assad by what he does, not by what he says. And we cannot sit back and wait any longer."
Burhan Ghalioun, leader of the opposition SNC, called for the strengthening of Syrian rebel forces as well as the setting up of "security corridors" inside Syria, a reference to internationally protected zones on Syrian territory that would allow the delivery of aid to civilians.
In a statement, the Syrian National Council said weapons supplies to the opposition were not "our preferred option" because of the risk they could escalate the killing of civilians, but it appealed for technical equipment to help rebels coordinate.
However, the nations meeting in Istanbul have so far failed to agree on such an intervention, which could involve the risky deployment of foreign security forces.
Syria blasted the conference, calling it part of an international conspiracy to kill Syrians and weaken the country.
A front-page editorial in the official al-Baath newspaper called it a "regional and international scramble to search for ways to kill more Syrians, sabotage their society and state, and move toward the broad objective of weakening Syria".
In-depth coverage of escalating violence across Syria
In Istanbul, police used tear gas and batons to disperse a group of about 40 Assad supporters who tried to approach the conference building. Many held portraits of the Syrian leader. One man waved Chinese and Russian flags.
The delivery of humanitarian aid to Syria's beleaguered civilians is a key provision of Annan's plan. Clinton announced $12m in additional aid for Syria's people, doubling the total American assistance so far.
Germany, whose foreign minister, Guido Westerwelle, attended the Istanbul meeting, said it was nearly doubling its humanitarian contributions to $7.6m.
But a comprehensive solution did not appear imminent without the cooperation of the Syrian government, whose military assaults on towns and cities have forced hundreds of thousands of people to flee their homes.
Tens of thousands of Syrian refugees have fled to neighboring Turkey, Lebanon and Jordan.
There are concerns that foreign intervention, even if it has a humanitarian goal, could widen the conflict by dragging in other countries and triggering a surge in sectarian tensions.