"The British government has told us that the constitution of Great Britain bars extradition of a person to a place where his life is in danger or he faces the death penalty", Moreno said in a radio interview.
Last month, Assange was charged in the United States, as unsealed court documents had inadvertently revealed his name.
Moreno didn't say he would force Assange out, but said the Wikileaks founder's legal team is considering its next steps.
Assange could be questioned in the investigation by Special Counsel Robert Mueller into possible Russian interference in the 2016 election that brought President Donald Trump to office. However, the Ecuadorian President has ramped up the pressure on Assange to leave the Ecuadorian embassy.
Camera IconA woman walks past the Ecuadorean Embassywhere Julian Assange has been living under asylum since
USA prosecutors last month inadvertently revealed the existence of a sealed indictment against Assange, according to WikiLeaks, but it was not known what the actual charges were.
"The suggestion that as long as the death penalty is off the table, Mr Assange need not fear persecution is obviously wrong", said Mr Pollack. He faces charges of espionage, conspiracy, theft of government property, and computer fraud in the U.S., and Donald Trump's administration has stated that the Wikileaks founder's arrest is a top priority.
Last year Jeff Sessions, the former United States attorney general, said arresting Mr Assange was a priority.
Sweden has since dropped that case, and Ecuador says there are no pending extradition requests against the WikiLeaks founder.
Mr Assange has denied any connection to Russian Federation.
Assange has been holed up in the Ecuadorian embassy since 2012, when he was granted asylum while facing allegations of sex crimes in Sweden that he said were a guise to extradite him to the U.S.