The WikiLeaks founder, Julian Assange, says he is fit enough to spend another five years inside the tiny Ecuadorean embassy in London, Ecuador's foreign minister said on Monday, as it was announced that British and Ecuadorean legal experts would try to resolve the impasse.

Despite the news of the legal talks – which followed a meeting on Monday morning between the British foreign secretary, William Hague, and his Ecuadorean counterpart, Ricardo Patiño – neither London nor Quito is showing any sign of backing down.

The Foreign Office said "no substantive progress" had been made during the discussions, while Patiño told a press conference that Assange's situation was "totally unjust".

Patiño said his government and Assange himself were prepared for a long waiting game, with the WikiLeaks founder telling him he was fit enough to spend another five years inside the embassy, in which he will have been holed up for exactly a year on Wednesday.

Assange walked into the embassy in Knightsbridge last June in an attempt to avoid extradition to Sweden to face sexual assault and rape allegations, which he denies. Ecuador granted him political asylum two months later but the British authorities have made it clear that he will be arrested if he leaves the building.

Patiño expressed hope that the legal working party might find a solution to the impasse, but insisted his government would never abandon Assange.

"Our government will not hand Mr Assange over to the UK government nor to anyone else and we shall continue to stress that Mr Assange has the right to benefit from asylum," he said. "We feel he should be handed over into safe conduct so that he can leave the UK for elsewhere."

He said Assange had been deprived of his liberty for a year, adding: "Really, is justice prevailing here? It's not, is it?"

Patiño said: "For us this is a matter of principle rather than patience, and of course if you have strong principles you must have sufficient patience … When you act on principle, you have all the time in the world and that's what we've also committed to Mr Hague and Mr Assange."

He added: "We do hope that Mr Assange is not going to get older and die in our embassy."

A Foreign Office spokesman said: "Ministers agreed that officials should establish a working group to find a diplomatic solution to the issue of Julian Assange, but no substantive progress was made. The foreign secretary was clear once again that any resolution would need to be within the laws of the United Kingdom."

Patiño, who conceded that Scotland Yard's round-the-clock guarding of the embassy was sometimes "a bit uncomfortable" for staff, said the police and the British government could rest assured that Ecuador would make no attempt to whisk Assange from the premises.

"We're not going to smuggle Mr Assange out in the boot of a car or through an underground tunnel or something," he said. "The Ecuadorean government isn't going to go out through the back door, we're going to come out proud through the front door … We're going to ensure that he comes out facing his freedom – the freedom of our country. This is what we are hoping for."

He said Assange was in good spirits and they had been up until 4am on Monday talking about the situation.

"He said he was strong enough to stay in our embassy for at least five years if he is not granted safe passage," Patiño said. "[But] I would consider it a total injustice if he has to spend more time in our embassy."

Asked whether Quito would countenance a similar request for asylum from the NSA whistleblower, Edward Snowden, Patiño said the government would certainly consider it.

"If he applies to our government, then of course we shall analyse the situation and of course other countries may be involved too," he said. "But if he applies for asylum to the Ecuadorean government, then, shouldering its full responsibility, the Ecuadorean government will analyse the request."