The shift came after more than a year of faltering US-led efforts to oust the leftist Mr Maduro.
Mr Guaido came under growing pressure from authorities, who on Tuesday summoned him to answer charges of attempting a coup.
The US secretary of state, Mike Pompeo, said that as part of a new “democratic transition framework”, bitter rivals Mr Maduro and Mr Guaido should set up an interim government with members of both their parties that will arrange elections in six to 12 months.
The person who heads the transitional government would not be allowed to run for president.
If fully implemented, the US and European Union would then lift sanctions, including sweeping US restrictions on Venezuela’s vital oil exports and on Mr Maduro and his allies as individuals, the State Department said.
In addition, the IMF and other international lenders would be invited to consider economic relief for Venezuela, from which millions have fled as they face dire shortages of food and other necessities.
The plan also calls for the departure of foreign forces from Venezuela, a reference to the regime’s support from Cuba and Russia.
Mr Pompeo urged all sides to consider the proposal “carefully and seriously”.
“We believe this framework protects the interests and equities of all Venezuelan people who desperately seek a resolution to their dire political, economic and humanitarian crisis, and who know Venezuelans can have something better,” he said
On Twitter, Mr Pompeo said: “Today the US presented a framework for a democratic transition as a clear, equitable, and common sense path to end the political crisis in Venezuela. Economic pressure will continue until Maduro accepts a genuine democratic transition.”
The proposed framework is not without stumbling blocks. Mr Maduro has repeatedly ruled out stepping aside, and Mr Guaido proposed a transitional government in failed talks brokered by Norway in 2019.
Mr Pompeo signalled that US goals have not changed, saying that Washington still wants Mr Maduro out of office and still supported Mr Guaido.
The 36-year-old engineer is recognised as interim president by the US and some 60 other countries.
Today the U.S. presented a framework for a democratic transition as a clear, equitable, and common sense path to end the political crisis in #Venezuela. Economic pressure will continue until Maduro accepts a genuine democratic transition.
— Secretary Pompeo (@SecPompeo)
“I think he’s the most popular politician in Venezuela. I think if there were an election held today, he could do incredibly well,” Mr Pompeo said. “But more importantly we continue to support him. When we put together this pathway to democracy, we work closely with him.”
Elliott Abrams, the US pointman on Venezuela, said that Mr Guaido would remain head of the National Assembly — a position from which he derives his legitimacy following wide allegations of fraud in Mr Maduro’s 2018 re-election.
On Twitter, Mr Guaido welcomed Mr Pompeo’s initiative: “This is the time to rise; we are taking the right steps to save Venezuela.”
Hours earlier, Venezuelan attorney general Tarek Saab said on state television that Mr Guaido had been summoned to appear before prosecutors in an investigation into the seizure of weapons in neighbouring Colombia that were allegedly destined for Venezuela.
The cache of weapons is said to be linked to a retired Venezuelan general, Cliver Alcala — who last week surrendered to US authorities on drug-trafficking charges, pleading not guilty before a federal court in New York on Tuesday.
Mr Alcala was once close to the late president Hugo Chavez, Mr Maduro’s predecessor and ideological inspiration, but Mr Saab says he is now taking orders from Mr Guaido.
Just last week the US filed drug-trafficking charges against Mr Maduro, placing a $15 million bounty on his head.
With reporting from the AFP