QUITO, Ecuador — Ecuador’s president on Thursday ramped up the pressure on Julian Assange to leave his country’s embassy in London, saying Britain had provided sufficient guarantees that he would not be extradited to face the death penalty abroad.

Mr. Assange, the founder of WikiLeaks, has been holed up in the Ecuadorean Embassy since 2012. He was granted asylum there while facing allegations of sex crimes in Sweden that he said were a guise to extradite him to the United States.

President Lenín Moreno’s comments in a radio interview Thursday suggested that months of quiet diplomacy between the Ecuador and Britain to resolve Mr. Assange’s situation is bearing fruit — even as questions are swirling about his legal fate in the United States.

“The road is clear for Mr. Assange to take the decision to leave,” Mr. Moreno said, citing written assurances he said he had received from Britain.