GENEVA -- Syrian government anger over a U.S. decision to resume aid to the opposition prompted the U.N. mediator to cut short Tuesday's peace talks, but he said no one was to blame for the impasse and that the negotiations would continue.

A deal to allow humanitarian aid into Homs remained stalled, with the Syrian delegation demanding assurances the U.S. aid will not go to "armed and terrorist groups" in the besieged city.

U.N.-Arab League mediator Lakhdar Brahimi said he was relieved that the government and opposition said they will remain in the daily talks through Friday, as planned.

"Nobody's walking out. Nobody's running away," he told reporters. "We have not actually made a breakthrough, but we are still at it, and this is enough as far as I'm concerned."

Tuesday's talks were the fifth day of negotiations regarding the civil war, focusing on opposition calls for the formation of a transition government in Syria and help for Homs.

But there has been little progress toward resolving a key issue of whether President Bashar Assad should step aside and transfer power to a transitional government.

Russian Foreign Minister Sergey Lavrov, whose country has been a key Syrian ally, said Moscow wants to avoid "another obsession with regime change because of somebody's personal animosity, personal hatred to a particular individual."

"Imagine Assad disappears. Who is going to keep it together? There is no answer," Lavrov said in Brussels, where a Russia-European Union summit was being held.

Brahimi said he decided to cut short Tuesday's talks "without any request or pressure from anyone."

He confirmed that the Syrian government delegation had talked at length about its opposition to the resumption of U.S. aid.

"We believe this is not the best present to the Geneva conference," said Faisal al-Mikdad, Syria's deputy foreign minister, calling the American decision "another manifestation of U.S. support for "terrorist groups" in Syria.

"This proves again that the United States is not interested in the success of this process, and we believe the U.S. has to desist and stop its claims that it is interested in the success of this conference," he told reporters.

American officials said Monday the U.S. has restarted deliveries of nonlethal aid to the Syrian opposition, more than a month after al-Qaida-linked militants seized warehouses and prompted a sudden cutoff of Western supplies to the rebels.

The officials said the communications equipment and other items are being funneled only to non-armed opposition groups, but the move boosts Syria's beleaguered rebels, who saw their international support slide, in large part because of the extremists among their ranks.

"Any notion that we support terrorists is ludicrous. The Assad regime is a magnet for terrorists," U.S. State Department spokesman Edgar Vasquez said in a statement.

Vasquez accused the Syrian government of "evading the core purpose of the Geneva talks," which is to reach a negotiated political solution for ending the war and suffering of Syrians.

Brahimi opened the morning session reviewing the principles of the Geneva Communique of June 2012, a broad but ambiguous proposal endorsed by Western powers and Russia to provide a basis for negotiations. Assad's role in any transitional government was a red line during those negotiations and left vague. The U.S. and Russia disagreed about Assad's role, but they signed the communique.

Murhaf Joueijati, a member of the opposition Syrian National Coalition's negotiating team, said Tuesday's session was cut short to give Syria time to make its proposal about the future of the country within the context of the 2012 accord.

On Monday, the government presented a working paper on Syria's future, which Joueijati said the opposition rejected because it "had nothing to do with a transitional government."

Assad's family, from Syria's Alawite minority, has ruled the country since 1970, pulling other religious minorities into its political orbit while rebellions by members of the Sunni majority were crushed. Today's civil war began as a peaceful uprising for freedom and rights in March 2011, but it has deepened the country's sectarian divide and that could add to the difficulties of forming a transitional government.

Joueijati accused the government of holding up the delivery of aid to Homs, which has been under siege for nearly two years.

One complication in doing that and evacuating the city's residents is that the opposition delegation does not control armed groups inside Syria, including al-Qaida-backed militants, who do not feel bound by agreements reached in Geneva. These groups gained control of Syria's uprising as it evolved into an insurgency.