LONDON — A British judge upheld the arrest warrant for the WikiLeaks founder Julian Assange on Tuesday, assuring that he would remain ensconced in the Ecuadorean Embassy, where he has been for the past five and a half years.

The judge, Emma Arbuthnot, did not immediately explain her reasons, saying only, “I am not persuaded that the warrant should be withdrawn.”

After the ruling, one of Mr. Assange’s lawyers, Mark Summers, asked whether it was in the public interest to keep pursuing his client for breach of bail.

“Normally,” Judge Arbuthnot said, “such issues would only be considered if somebody were brought to court to explain their failure to surrender to bail.”