LONDON (AP) — A lawyer says one of the prime suspects in the killing of Alexander Litvinenko may not testify as planned next week at an inquiry into the former Russian spy's death.

Counsel to the inquiry Robin Tam said Friday that Dmitry Kovtun claimed he was bound by obligations of confidentiality to an ongoing Russian investigation. Kovtun was due to testify Monday by video link from Russia to the British inquiry, headed by judge Robert Owen.

Litvinenko, a former KGB officer, died in London in 2006 after drinking tea laced with radioactive polonium. On his deathbed, Litvinenko accused Russian President Vladimir Putin of ordering his assassination.

British police have accused Kovtun and another Russian man, Andrei Lugovoi. Both deny involvement.

Owen gave Kovtun until noon Monday to decide whether to participate.