A Swedish appeals court has rejected Julian Assange's request to have his arrest order set aside.

Swedish prosecutors want to question the WikiLeaks founder over alleged sex crimes.

The Court of Appeal on Thursday agreed that "there is a great risk that he (Assange) will evade legal proceedings or punishment".

But the court provided some hope for the Australian - who's holed up in Ecuador's embassy in London - by noting the investigation into the suspected crimes had come to a halt.

The court said it "considers that the failure of the prosecutors to examine alternative avenues is not in line with their obligation - in the interests of everyone concerned - to move the preliminary investigation forward".

Assange's legal team argues Swedish prosecutors have dragged out the case for an unreasonably long period by not interviewing him at the embassy in the UK.

His lawyers insist the circumstances of his stay at the diplomatic mission constitute a deprivation of liberty.

But the Court of Appeal in Stockholm noted "the fact is Julian Assange can leave the embassy if he so wishes".

The Australian was more successful arguing the European arrest warrant was disproportionate because prosecutors weren't moving the investigation forward.

The appeal court noted "that higher demands must be made on the reasons put forward by the prosecutor in support of their request for detention, the longer the period of time that passes without the prosecutor moving the preliminary investigation forward".

That statement will give Assange hope that the current stand-off won't be allowed to drag on indefinitely.

For now, however, the appeal court was swayed by the fact Assange was suspected of relatively serious crimes and there was still a great risk he would flee if the warrant was set aside.

"These circumstances mean that the reasons for detention still outweigh the intrusion or other detriment entailed by the detention order.

"Thus there is, at present, no reason to set aside the detention order."

The court on Thursday further rejected Assange's request for copies of the text messages of the two women he's suspected of sexually assaulting.

It said his defence team had been allowed to see them which meant his right to insight had been satisfied.

The detention order was originally issued in late 2010.

After losing a UK legal battle against extradition Assange entered the Ecuadorian embassy in June 2012 and was granted political asylum two months later.