Sweden's sexual assault inquiry on Julian Assange is being pinched by time, with the statute of limitations about to expire on one charge and investigators unable to access Ecuador's embassy in London to question the WikiLeaks founder.

Swedish prosecutors petitioned the Ecuadorian embassy in June to interview Assange, who has been holed up in Quito's London mission since 2012 to avoid extradition to Sweden on allegations of rape and sexual assault -- charges Assange vehemently denies.

But access has thus far been delayed on procedural grounds, leading some people involved in the case to suspect Ecuador of playing the clock until mid-August, when the statute of limitations on the sexual assault accusation will expire.

"I am very critical of Ecuador's position. It can't really be said they did what they could to allow Sweden to question Assange," said Claes Borgstrom, a lawyer for one of the two women who accuse the WikiLeaks founder of having assaulted them in 2010.

Swedish prosecutors initially insisted Assange return to Sweden for interrogation -- a condition the 44-year-old Australian rejected on fears Stockholm could deliver him to US authorities, who may try him for leaking nearly 750,000 classified military and diplomatic documents in 2010.

In response to his enduring embassy asylum, Swedish prosecutors in March agreed to Assange's compromise offer to question him inside the London mission, but have yet to see their requests to see him approved by Ecuador.

If Swedish justice authorities are not allowed to question Assange before the statute of limitations on the sexual assault charges expire on August 13 and 18, Borgstrom said he was pretty sure the case will be dropped.

"If the statute of limitations expires, and most indications are that it will, the prosecutor will close the investigation," he said.

Should that happen, however, the inquiry would continue into the accusation of rape, which carries a 10-year statute of limitations and therefore expires in 2020.

- Late request -

Attorneys for Assange say suspicions that Quito is using delaying tactics are unfounded.

"The (Swedish) request came in late and is being processed by Ecuador, which will certainly approve it after following its own procedures," Assange's Swedish lawyer Per Samuelsson told AFP.

"It's wrong to claim Ecuador is trying to delay the process. Even the president has said he wants the questioning to take place."

Samuelsson added that playing down the clock is of no interest to Assange, who has repeatedly said the sexual encounters in the case were consensual.

"(He) doesn't think in terms of statutes of limitation. He's innocent, and wants to be questioned as soon as possible."

Ecuador's Foreign Minister Ricardo Patino criticised what he described as Sweden's expectation that access to Assange be tailored to its own changing schedule.

"I do not find it acceptable that ... (having) finally decided to answer the calls during all these years to continue the case, they would expect the role of Ecuador would be limited to opening the doors of its embassy," Patino told The Guardian.

Sven-Erik Alhem, a former prosecutor and head of a Swedish association supporting victims of crimes called Ecuador's position and the failure to grant timely access to Assange "surprising".

"If both countries want justice done, and Assange himself wants to be questioned, there's no reason for the interrogation not to take place." afp