BEIJING — Senior Chinese and American officials concluded two days of negotiations on Friday with no deal and no date set for further talks, as the United States stepped up its demands for Chinese concessions to avert a potential trade war.

The American negotiating team, which included Treasury Secretary Steven Mnuchin and the United States trade representative, Robert E. Lighthizer, headed for the airport after the talks and did not release a statement. But a list of demands that the group took into the meeting called for reducing the United States’ trade gap with China by $200 billion over the next two years and a halt on Chinese subsidies for advanced manufacturing sectors.

The demands, which spread on Chinese social media and were confirmed by a person close to the negotiations, suggested that both sides hardened their positions this week despite the two days of talks. Senior Chinese officials and their advisers were also sending a deliberate message to the West that the days of Beijing being conciliatory were over, and that China was staking out its own position in the negotiations.

The person close to the negotiations insisted on anonymity because of diplomatic sensitivities.

The extensive list of United States trade demands was unexpectedly sweeping, and showed that the Trump administration has no intention of backing down despite Beijing’s assertive stance in the last few days. “The list reads like the terms for a surrender rather than a basis for negotiation,” said Eswar Prasad, an economics professor at Cornell University.