Ecuador's minister for foreign affairs, Ricardo Patino, has released details of a letter he said was delivered through a British embassy official in the capital of the South American country, Quito.
The letter said:
You need to be aware that there is a legal base in the UK, the Diplomatic and Consular Premises Act 1987, that would allow us to take actions in order to arrest Mr Assange in the current premises of the Embassy.
We sincerely hope that we do not reach that point, but if you are not capable of resolving this matter of Mr Assange's presence in your premises, this is an open option for us.
It went on:
We need to reiterate that we consider the continued use of the diplomatic premises in this way incompatible with the Vienna Convention and unsustainable and we have made clear the serious implications that this has for our diplomatic relations.
WikiLeaks founder Julian Assange has spoken for the first time since taking refuge in the Ecuadorian embassy in London.
It is remarkable how much strain there is between the UK and Ecuador over the fate of a man who is facing charges in neither country.
The UK and Ecuador are locked in a diplomatic standoff over WikiLeaks founder Julian Assange. Here is some legal background.