Venezuela¡¯s President Nicolas Maduro is running out of options to step down and leave his country under U.S.-guaranteed safe passage, following a short call with U.S. President Donald Trump last month where Trump refused a series of requests from the Venezuelan leader, according to four sources briefed on the call.

The call, on Nov. 21, came after months of increasing U.S. pressure on Venezuela, including strikes against alleged drug-smuggling boats in the Caribbean, repeated threats by Trump to extend military operations to land and the designation of Cartel de los Soles, a group the Trump administration says includes Maduro, as a foreign terrorist organization.

Maduro and his government have always denied all criminal accusations and say the U.S. is seeking regime change to take control of Venezuela¡¯s vast natural resources, including oil.