CAIRO, Sept 19 (Reuters) - Egypt has returned to Qatar $2 billion that the Gulf state had deposited with Egypt's central bank, after negotiations to convert the funds into three-year bonds broke down, central bank Governor Hisham Ramez said by telephone on Thursday.

Qatar had sent Egypt $3 billion in May, of which it converted $1 billion into three-year bonds.

Cairo's relations with Qatar deteriorated after the Egyptian army deposed President Mohamed Mursi on July 3. Qatar had been a firm backer of Mursi's Muslim Brotherhood and lent or gave Egypt $7.5 billion during the year he was in power.