"If they had accepted Ecuador's offer to question him (at the embassy) 1,000 days ago, it would have saved us all a lot of money and trouble," Foreign Minister Ricardo Patino wrote on Twitter.
"On Monday Assange will mark 1,000 days inside our embassy in London. From the first day we have offered to let (prosecutors) question him and they didn't do it," he tweeted.
"The reason for taking Assange's statement now, after 1,000 days, is the statute of limitations. And if the statute of limitations were five years from now?"
He has been there ever since, saying he fears Sweden will extradite him to the United States, where an investigation is ongoing into WikiLeaks' release of 500,000 classified military files on the wars in Iraq and Afghanistan and 250,000 diplomatic cables.
The mass leak in 2010 deeply embarrassed Washington.
The lead prosecutor in the Swedish case, Marianne Ny, said she had reluctantly agreed to question Assange at the Ecuadoran embassy because the statute of limitations on some of the charges will expire in August.