The museum's Oxus, or Amu Darya, collection consists of about 170 objects, dating mainly from the fifth and fourth centuries B.C., from the time of the Achaemenid Empire, when Persian control stretched from Egypt and the Aegean to Afghanistan and the Indus Valley.
British Museum spokeswoman Hannah Bolton said the collection had been put together from pieces bought at Indian bazaars, but that the origins of those items were hard to trace.
The treasures are believed to have been found in an area that is part of modern-day Tajikistan, in 1877. They were subsequently brought by merchants to the bazaars of India's Rawalpindi, where they caught the eye of Sir Alexander Cunningham, director general of the Archaeological Survey of India, and Sir Augustus Wollaston Franks, a museum curator and a benefactor.
Earlier on Thursday, Tajik President Emomali Rakhmon said every effort should be made to arrange for the Oxus collection to be brought back to the country for temporary display, and to subsequently be repatriated.
But Bolton said the British Museum had received no formal enquiry from Tajikistan on the possibility of a handover, and that it was therefore premature to discuss the matter.
The Oxus treasures include objects such as coins, vessels, a gold scabbard, model chariots and figures, armlets, seals, rings and medallions, and are considered to be the most important surviving collection of Achaemenid Persian metalwork.
