Scotland Yard detectives investigating the murder of Wpc Yvonne Fletcher are expected to be able to visit Libya "soon".
The commitment of the National Transitional Council to co-operate with the investigation into the 1984 killing was reaffirmed last week during a visit to London by interior minister Fawzy Abdilal.
A senior British diplomat said: "The investigation is open. The main focus for us is to ensure the police can take forward that investigation. That is why we have consistently raised it with the Libyan authorities.
"They have been very positive about this and, whilst we can't put an exact time on it, we hope that the police will be able to visit Libya soon."
Wpc Fletcher was killed when diplomats inside the Libyan embassy in London opened fire on an anti-Gaddafi protest outside the building.
Two of the diplomats suspected to have been involved in the killing are reported to have since died, including the junior official suspected of firing the fatal shot who has been named as Abdulmagid Salah Ameri.
A third suspect - named in reports as Matouk Mohammed Matouk - is reported still to be alive and is likely to be the focus of the police inquiry.
The issue of the murder investigation - as well as the Lockerbie bombing and Colonel Gaddafi's arming of the IRA - were raised with Mr Abdilal during a series of high level meetings, including with Foreign Office minister Jeremy Browne and national security adviser Sir Kim Darroch.
Diplomats said that Mr Abdilal - who was visiting the UK ahead of the first anniversary next week of the start of the Libyan uprising which led to Gaddafi's overthrow - had been clear in his commitment to the inquiries.
One senior diplomat said: "This is an issue which we have raised at pretty much every high level meeting that we have had. He said he was very happy for his ministry and others to co-operate with us on these issues. The commitment is there to work with us. We are more optimistic than we were a year ago."
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