Scotland Yard is trying to locate the skeleton of a 70-million-year-old dinosaur, which has been stolen and is believed to be in Britain.
The Mongolian government has sought the help of UK police in finding the rare Tarbosaurus Bataar, a close relative of the Tyrannosaurus Rex. On the black market, the dinosaur fossil could fetch around £700,000.
After details came to light of its theft during a US court case, Oyungerel Tsedevdamba, Mongolia's Culture Minister said: "We hope the British police authorities will collaborate with Mongolia on this important case that will help stop the illegal smuggling of dinosaur fossils."
In December 2012, Florida-based fossil trader Eric Prokopi pleaded guilty to three counts of illegally trafficking dinosaur bones out of Mongolia and China.
He is due to be sentenced on 25 April and faces up to 17 years in jail, with a £160,000 fine.
Five dinosaur skeletons have already been recovered in the United States.
A sixth remains missing and, according to prosecution documents, the Tarbosaurus fossil could be in Britain.
UK police are seeking to interview a British trader about the missing 40ft dinosaur skeleton.
The Tarbosaurus, whose name translates as "alarming lizard", was one of most ferocious predators in the area that is now Mongolia's Gobi Desert.
The dinosaur measured up to 12m long and was equipped with 64 flesh-ripping teeth.
Prokopi moved the dinosaur parts out of Mongolia via Britain by falsifying paperwork before exporting them to the US.
Mongolian officials believe British fossil trader Chris Moore could help with the search.
Moore, based in Devon, has business links with Prokopi which came to light in the US court case.
According to an invoice seen by the Daily Star, Moore sent three crates which were marked "fossil reptiles" to Prokopi in Florida in March 2010, valued at £9,300.
But US prosecutors claim the shipment contained the bones of a 24ft Tyrannosaurus which originated from Mongolia and was sold at a New York auction house for £655,000 last May.
The skeleton has since been seized, along with the other recovered fossils and is waiting to be sent back to Mongolia for display in a museum.
The Mongolian authorities say Moore, who has not been accused of any wrongdoing, visited the country with Prokopi in 2011 and went fossil digging in the Gobi Desert.
Preet Bharara, the US Attorney who worked on the case, said: "Fossils and ancient skeletal remains are part of the fabric of a country's natural history and cultural heritage, and black marketeers like Prokopi who illegally export and sell these wonders, steal a slice of that history.
"We are pleased that we can now begin the process of returning these prehistoric fossils."
The location of the Tarbosaurus Bataar remains a mystery.