Any direct contact between Washington and Mr. Maduro would risk sidelining parallel negotiations — that are mediated by Norway and held in the Caribbean island of Barbados — between the Venezuelan government and opposition officials led by Juan Guaidó, whom the United States views as Venezuela’s rightful president.

Those negotiations allow Mr. Maduro to claim he is seeking a peaceful resolution of the crisis and have helped stave off tougher European sanctions. The talks also are the opposition’s best chance to unseat Mr. Maduro after months of diminishing mass rallies and failed attempts to split his government.

The Barbados negotiations began gaining traction in July, after Mr. Maduro offered the opposition new presidential elections in return for the lifting of American sanctions. But he suspended the talks in protest of new American sanctions issued Aug. 5 that blocked all Venezuelan public assets in the United States.

The sanctions, which surprised both Mr. Maduro and opposition leaders, also threaten economic penalties against any foreign company doing business with the Venezuelan government. Mr. Abrams maintained on Tuesday that the United States would not lift sanctions against Venezuela unless Mr. Maduro steps down.

Officials close to both sides of the Venezuelan negotiations said the talks could resume in Barbados as soon as next week, although no date has been set. They discussed sensitive topics on the condition of anonymity.

“The more the United States gets involved in Venezuela, the more problems it creates for the negotiation process,” said Temir Porras, a former chief of staff to Mr. Maduro who now works as a political consultant in Caracas. “The United States pursues a policy that has a lot of influence on Venezuela’s future, but it’s unable to resolve the crisis. It can only be resolved by Venezuelans.”

Mr. Abrams said the Trump administration would not support new national elections with an incumbent — either Mr. Maduro or Mr. Guaidó — on the ballot. If either man wanted to run for the presidency, Mr. Abrams said, he should first leave office to prevent concerns about election tampering by the government.