GENEVA — New fireworks erupted at talks between the Syrian government and the opposition here on Tuesday, as the government sharply criticized a recent decision by the United States Congress to approve continued support for the Syrian rebels, and the United Nations’ top mediator decided not to continue talks in the afternoon.

The opposition delegation presented a detailed plan for the future of Syria, said Oubai Shahbandar, an adviser to the delegation. But after what Mr. Shahbandar called an “outburst” from the government’s lead negotiator, Bashar al-Jaafari, no further discussion was held on forming a transitional government, the central issue in the talks under the protocols of the first Geneva conference, in 2012.

Syria’s information minister, Omran al-Zoubi, played down the clash in the morning meeting, saying in an interview that the two sides had spent “10 minutes laughing” after Mr. Jaafari, the Syrian ambassador to the United Nations, joked that Al Jazeera, the Qatari-owned pan-Arab news channel that the government despises for its sympathetic stance on the insurgency, was “founded by Gandhi and Nelson Mandela.”

Mr. Zoubi said the American aid to the rebels, now with explicit congressional approval, contradicted the United States’ role as a sponsor of the peace talks. Russia, the other sponsor, has supported the Syrian government with arms sales, but Syrian officials say that falls under legal bilateral relations and is not equivalent to the American funding.