Germany, France, Spain and Britain were also among the nations calling on Mr. Maduro to commit to a new vote. Mr. Maduro’s re-election last year was marred by reports of widespread coercion and fraud.

Mr. Arreaza, the foreign minister, scoffed at the ultimatum.

“Europe is giving us eight days? What gives you the right?” Mr. Arreaza demanded during a session of the United Nations Security Council.

Mr. Maduro continued to strike a defiant tone on Saturday, writing on Twitter that his government “would not rest until we defeat the attempted coup” orchestrated by people who want to establish a “puppet government of the United States empire.”

But his government appears to have decided for the time being not to detain Mr. Guaidó or disrupt his political rallies as support for the 35-year-old opposition leader has grown at home and abroad. Mr. Guaidó proclaimed himself the legitimate head of the executive branch on Wednesday as his supporters took to the streets in droves.

He argued that the presidency became technically vacant on Jan. 10, when Mr. Maduro was sworn in for a new term after an election widely seen as rigged. The country’s Constitution says that the president of the National Assembly, Mr. Guaidó in this case, becomes interim leader if the presidency is vacated.

Venezuela’s Foreign Ministry and the State Department did not respond to a request for information about the status of Venezuelan diplomats. It was unclear how many have pledged allegiance to Mr. Guaidó and whether they would remain accredited as diplomats in the United States.

At least one official, the country’s military attaché in Washington, Col. José Luis Silva, said in an interview with The Nuevo Herald that he no longer recognized Mr. Maduro as president.