(Adds Palestinian comment, edits) By Adam Entous JERUSALEM, Jan 18 (Reuters) - Israel will soon begin transferring $100 million in withheld Palestinian tax revenues to President Mahmoud Abbas, a Palestinian official said on Thursday. Senior Abbas aide Saeb Erekat said the money would be deposited in the president's bank account and would be given to private bodies, without elaborating which ones, and also used for humanitarian purposes. He said the transfer would occur soon but did not give a timeframe. Israeli officials, speaking on condition of anonymity, said the money would be given on Friday and that some of it was meant to help fund a U.S.-backed security programme. Erekat would not comment on the matter. "Its designated use is for humanitarian needs, as defined by the Palestinian president, and for the implementation of recommendations" by U.S. Lieutenant-General Keith Dayton, who is overseeing an American-led programme to strengthen Abbas's presidential guard, a senior Israeli official said. The official did not say what specific security projects the tax money would be used for. Israeli Prime Minister Ehud Olmert has been under U.S. pressure to take steps to strengthen Abbas, a moderate and his Fatah-dominated presidential guard, which have been involved in a power struggle with the governing militant group Hamas, which has been building up its own "Executive Force." OLMERT PROMISE During his first formal meeting with Abbas on Dec. 23, Olmert promised to hand over the funds and to remove West Bank roadblocks. Since Abbas's meeting with Olmert, the Palestinian president's allies have complained that Israel has been undercutting him by taking its time to deliver on its promises. Abbas, who met U.S. Secretary of State Condoleezza Rice in the West Bank city of Ramallah on Sunday, asked Washington to intervene. Rice held talks with Olmert on Monday in Jerusalem. The Israeli government decided last February to halt the tax revenue transfers, estimated at $50 million to $60 million per month, after Hamas Islamists beat Abbas's Fatah movement in parliamentary elections a year ago. A senior Israeli government official said the $100 million will not be used by Abbas to make the long-overdue salary payments to Palestinian public sector workers, hard hit by a Western and an Israeli embargo of the Hamas-led government. "They (Israeli and Palestinian negotiators) found a mechanism to make sure the money will not get to the Hamas government or the Hamas Finance Ministry," the official said. Hamas has struggled to govern since taking office in March under the weight of U.S.-led sanctions imposed because of its refusal to recognise the Jewish state, renounce violence and abide by interim peace deals.