Updated

U.S. Secretary of State Hillary Rodham Clinton expressed doubt Sunday about whether President Bashar Assad would ever adhere to a U.N.-sponsored peace plan to end Syria's year of bloodshed, and urged world solidarity against a regime that she said was waging war on its own people.

Clinton told the 60 nations attending the "Friends of the Syrian People" conference in Turkey that no one could "sit back and wait any longer," even as the United States refuses to entertain military options to intervene in the crisis. Instead, she urged unity behind a four-point plan that includes more sanctions, humanitarian aid, support for the opposition and the promise of justice one day for the Assad regime's willing accomplices in human rights atrocities.

"We meet at an urgent moment for Syria and the region," Clinton said.

International pressure forced Assad to agree to U.N. mediator Kofi Annan's six-point plan including an immediate a cease-fire, she noted, but said "nearly a week has gone by, and we have to conclude that the regime is adding to its long list of broken promises."

The meeting aims to further isolate Assad's government and bolster a divided Syrian opposition. The United States and its European and Arab allies have papered over some of their own disagreements on how best to advance the cause of the opposition and help bring about the regime's collapse, with countries agreeing for now to hold off on military options from directly arming the anti-Assad rebels to creating buffer or safe zones within Syria for them to operate.

Clinton lamented that Assad promised to pull his regime's forces back, silence its heavy weapons, allow peaceful demonstration and access for humanitarian aid and journalists. He also should begin a political transition, she said.

But, "rather than pull back, Assad's troops have launched new assaults on Syrian cities and towns," she said. "Rather than allowing access for humanitarian aid, security forces have tightened their siege of residential neighborhoods in Homs and elsewhere. And rather than beginning a political transition, the regime has crushed dozens of peaceful protests."

Annan has urged the Syrian government to lay down its arms first, a challenge Assad's loyalists are rejecting. On Saturday, Foreign Ministry spokesman Jihad Makdessi said the government will not pull tanks and troops from towns and cities engulfed by unrest before life returns to normal there, describing the military's actions as those to reinforce "stability."

Activists reported fresh violence Saturday that killed more than two dozen people. The U.N. estimates more than 9,000 people have been killed since the uprising to oust Assad began in March 2011.

Clinton said Syrians will continue to defend themselves until Assad halts the violence. She said they should simultaneously build momentum "toward a new Syria: free, unified and at peace."

The U.S. and other countries are trying to help a splintered opposition coalesce. As part of that effort, they are helping the leading Syrian National Council restructure itself to be more transparent and inclusive so that minority and other groups still supportive of the Assad regime will break ranks. For those groups wishing to remain outside the SNC, Washington hopes they'll at least unite around a "common vision for a free, democratic and pluralist Syria that protects the rights of all citizens and all communities."

Clinton also announced $12 million in additional aid for Syria's people -- doubling the total American assistance so far. And she said the U.S. was providing communications equipment to help opposition members in Syria organize, remain in contact with the outside world and evade regime attacks.

The Obama administration is also championing a new program to ensure accountability for individuals who commit atrocities in Syria, should the regime fall. The program works as a kind of database that allows Syrians to document abuses, identify perpetrators and store evidence for future investigations and prosecutions.

"Our message must be clear to those who give the orders and those who carry them out," Clinton said. "Stop killing your fellow citizens or you will face serious consequences. Your countrymen will not forget, and neither will the international community."