British detectives probing the 1984 murder of a policewoman outside the Libyan embassy in London have been granted visas to pursue the investigation in Libya, police said.
Cameron said it was a "really positive step forward" in the hunt for her killers.
Fletcher, 25, was shot dead outside the Libyan embassy while policing peaceful demonstrations. No one has ever been charged with her murder.
The fatal shot was always believed to have been fired from inside the building, sparking an 11-day stand-off with police.
However, the killer was presumed to have left Britain among the 30 staff who were then deported under diplomatic immunity.
Kib said Tripoli would work "very closely" with London to resolve outstanding questions about the murder.
He worked with the opposition while in exile during Kadhafi's rule and said he knew some of those involved in the demonstration.
"The Fletcher case is a case that is close to my heart personally. I had friends who were demonstrating that day next to the embassy.
"It is a sad story. It is very unfortunate that it has anything to do with the Libyan people.
"I am here to tell you that we will work very closely together to resolve anything related to that issue."
The British government believes the overthrow of Libyan leader Moamer Kadhafi's regime has given investigators a much better chance of bringing a suspect to justice.
The killing led to Britain severing diplomatic relations with Libya until 1999 and has been a long-running sore in ties between London and Tripoli, along with the 1988 bombing of a passenger jet over the Scottish town of Lockerbie.
"I am absolutely delighted that we are working so closely together on issues of mutual interest, including having a Metropolitan Police team going to Libya to continue the investigation into the murder," Cameron said.
"I think that is a really positive step forward and I know it will be welcomed by everyone in Britain."
Source: AFP European Edition