KARACHI (Reuters) - Pakistans foreign exchange reserves fell to $16.39 billion in the week ending Dec. 4, down from $16.74 billion the previous week, the State Bank said on Thursday. Reserves held by the State Bank of Pakistan (SBP) fell to $12.65 billion from $12.97 billion in the week ending Dec. 4, and those held by commercial banks also eased to $3.74 billion from $3.77 billion, said the State Bank of Pakistan. The State Bank of Pakistans reserves fell due to debt payments, said Syed Wasimuddin, chief spokesman of the central bank. Pakistans reserves hit a record high of $17.10 billion in the week ending Oct. 15 because of an increase in remittances from overseas Pakistanis and a narrowing trade deficit. Earlier the reserves got a boost in September after the IMF sent Pakistan $450 million and said that the money would go toward the budget to help with additional spending for flood relief and immediate foreign exchange needs. This was separate from the $11 billion IMF bailout programme, agreed in 2008. In May, Pakistan received $1.13 billion, the fifth tranche of the programme. The IMF is likely to delay the possible release of the sixth tranche because of the slow implementation of fiscal reforms.