Several days of high-level talks at the United Nations failed to significantly advance diplomatic efforts to stem the spreading violence in Syria, where more than 300 people were killed in a single day this week, according to opposition activists.

The diplomatic deadlock left frustrated policymakers straining to give life to a set of ambitious but largely unrealistic plans to stop the bloodshed, including a French proposal for U.N.-protected safe havens in Syria and a Qatari plan to send a pan-Arab force into the country.

U.N. officials said there remained little prospect for a major diplomatic breakthrough as long as the warring Syrian factions remain committed to military victory and the United States and Russia remained divided over how to resolve the crisis.

World leaders gathering in New York this week for the annual General Assembly debate voiced increasing frustration at the United Nations’ feeble response to a conflict that has reportedly left more than 30,000 people dead, displaced as many as 1 million and sent more than 300,00 fleeing for refuge in Jordan, Iraq and Turkey. Conditions have sharply deteriorated as foreign governments, including Iran’s, Saudi Arabia’s and Qatar’s, have supplied arms to factions in the conflict.

On Friday, rebels launched a major assault to wrest control of Aleppo, Syria’s largest city, from government forces.

“What has the international community done to stop this carnage? Literally nothing,” Turkey’s foreign minister, Ahmet Davutoglu, complained in a speech before the General Assembly on Friday. “We have yet to see a single effective action to save innocent lives.”

In Washington, Defense Secretary Leon E. Panetta said that U.S. intelligence indicates that Syria has recently moved some of its chemical weapons, the security of which has been a top concern of U.S. officials. Panetta said it is believed the Syrian government moved them to ensure their safety, but he added that, in some cases, U.S. officials remain in the dark about where the materials have been taken.

American officials met Friday with representatives of about 90 governments — the so-called Friends of Syria — and of the Syrian opposition to explore ways to help the opposition prevail in its quest to oust the government of President Bashar al-Assad. But the Americans again made it clear they would not provide weapons or other military aid.

“Conditions in Syria continue to deteriorate as the Assad regime relentlessly wages war on its own people,” Secretary of State Hillary Rodham Clinton told reporters before the meeting. “And we see more bodies filling hospitals and morgues, more refugees leaving their homeland and flooding into neighboring countries.”

Clinton said the United States is concentrating its efforts on increasing humanitarian assistance, aiding the opposition and supporting efforts to deliver services and administer rebel-
controlled territory.

She announced an additional $30 million in aid to purchase food, water, blankets and medical services, bringing the total in U.S. humanitarian assistance to $130 million. She also pledged $15 million to supply opposition groups with satellite-linked computers, telephones and cameras, as well as training “to strengthen their networks, avoid regime persecution and document human rights abuses.”

“We are seeing the emergence of a free Syria, and the United States is directing our efforts to support those brave Syrians who are laying the groundwork for a democratic transition,” she said.

Lakhdar Brahimi, the U.N.-Arab League special representative to Syria, held intensive meetings this week with foreign ministers and world leaders in search of a strategy for a diplomatic transition. But he did not provide any public details on his strategy for peace.

On Monday, Brahimi provided a downbeat assessment of the prospects for peace, telling the U.N. Security Council that his efforts “cannot go anywhere” without a “strong, collective, united and sustained support from this council.” But he also expressed hope that “we will find an opening in the not-too-distant future.”

Brahimi has made it clear that any workable transition in Syria would require a “clean break with the past” — his strongest suggestion to date that he believes Assad must step aside. But he also underscored the importance of preserving Syria’s institutions, which have served the Assad dynasty.