LONDON - Britain’s Supreme Court on Wednesday denied WikiLeaks founder Julian Assange’s appeal against extradition to Sweden to face questions about allegations of rape, sexual assault, and unlawful coercion.

At a short hearing in central London, the president of the Supreme Court, Nicholas Phillips, said the court dismissed the defense team’s argument that the warrant that led to Assange’s arrest was flawed.

Speaking to a packed courtroom, Phillips said the case had “not been simple to resolve,’’ and was decided by a vote of 5 to 2.

In a surprise intervention, Assange’s legal team asked for - and was granted - two weeks to consider lodging an application to reopen the case. The lawyers said that the judges decided the case based on the Vienna Convention on the Law of Treaties, but that this point had not been discussed in court.

Assange - who shot to international fame when his antisecrecy website spilled official state secrets in the form of Afghanistan and Iraq military reports and a mammoth cache of diplomatic cables - did not appear in court on Wednesday. His lawyers told reporters he was stuck in traffic.

Swedish authorities want to question Assange - no charges have been brought - about separate encounters he had with two WikiLeaks volunteers. The volunteers say they had consensual sex with Assange, but at some stage, it became nonconsensual. One of the women, described in the courts here as “Miss B,’’ accused Assange of sexually assaulting her while she was asleep.

Although Assange insists the sex was consensual, his case before the Supreme Court hinged on a single technicality: Was the Swedish prosecutor who issued the European arrest warrant that led to his arrest in December 2010 a valid judicial authority?

Only a “competent judicial authority’’ can issue a European arrest warrant, a system ushered in to speed up extradition between European nations.

In a 161-page judgment, the Supreme Court haggles over what, exactly, is meant by the words “judicial authority,’’ ultimately rejecting Assange’s arguments that a public prosecutor cannot fall into the category.

Although the Supreme Court is Britain’s highest appellate court for civil cases, Assange has not yet exhausted all of his legal options.

Assange can still appeal to the European Court of Human Rights in Strasbourg, France, which would decide within two weeks whether to take the case.

If that court declined to take the case, Assange would be extradited to Sweden “as soon as arrangements can be made,’’ according to a statement by the Crown Prosecution Service. If the European court accepts the case, analysts say, the long-running legal battle could drag on for more weeks or months.

In February 2011, a lower court in Britain granted Sweden’s extradition request. Assange appealed the ruling and lost, but he won permission to appeal to the Supreme Court, which agreed to hear the case before seven judges - two more than normal - because, the court said, of the “great public importance of the issue raised, which is whether a prosecutor is a judicial authority.’’