Mr Assange, whose conditions included staying at his bail address between 2200 and 0800 BST, spent Tuesday night at the embassy.
Last week he failed to reopen an appeal against his extradition to Sweden.
Mr Assange, wanted for questioning over rape and sexual assault allegations, denies any wrongdoing.
Ecuador had said it was “studying and analysing” Mr Assange’s request for asylum.
Mr Assange fears if he is sent to Sweden it may lead to him being sent to the US to face charges over whistle-blowing website Wikileaks, for which he could face the death penalty.
His website has published a mass of leaked diplomatic cables that embarrassed several governments and international businesses.
BBC News legal correspondent Clive Coleman said Scotland Yard’s plan to arrest Mr Assange was “another extraordinary twist in a truly extraordinary tale”.
Mr Assange is on £200,000 bail, provided by several high-profile supporters including socialite Jemima Khan and Ken Loach, who each offered £20,000 as surety.
Our correspondent said that, as Mr Assange had broken the condition of his bail that he lived at a friend’s house in Norfolk, a criminal offence had been committed.
If the situation was resolved quickly by Ecuador “effectively putting him on the doorstep of the embassy” for police to arrest, he may not be prosecuted for the breach and the extradition to Sweden would take its course.
Mr Assange’s supporters would have to argue that, as it was always known exactly where Mr Assange was, they should have their bail money returned, our correspondent added.
But as it was with the court to provide security and bail had been breached, it was possible they would lose their money, he said