Jerusalem - Israel authorised the release of $11-million in frozen Palestinian taxes on Sunday in a bid to ease a humanitarian crisis ahead of Ehud Olmert's first trip to Washington as prime minister.

While both Israel and the United States are working to isolate the Hamas Islamists controlling the Palestinian government, the Jewish state has been under pressure to help avert the collapse of the Palestinian Authority.

Israeli political sources made clear that none of the tax funds to be released would reach the Palestinian Authority. Israel plans to use the money to buy medical supplies based on advice of a foreign auditor and transfer them to Gaza hospitals.

The $11-million to be freed up is part of $220-million in Palestinian tax and customs levies frozen by Israel to push Hamas to recognise the Jewish state, renounce violence and accept past peace accords.

Western donors have also cut aid and contacts to put pressure on Hamas, which is sworn to Israel's destruction and has refused calls to disarm.

Palestinian Authority spokesperson Ghazi Hamad Israel's decision on the funds, saying: "This is not an Israeli favour. (Israel) uses this as a blackmail for political concessions."

The United States is keen to bolster the more moderate Palestinian President Mahmoud Abbas as a partner for eventual peace negotiations. Olmert has indicated unilateral separation moves would be carried out if talks remain on ice.

Olmert cast doubt on Abbas's ability to lead negotiations with Israel, telling CNN's Late Edition that the Palestinian leader was "powerless" and "helpless" to stop militants.

But he also said he may speak to Abbas, possibly as early as when he returned from Washington, if he tried to change Hamas, disarm "terrorist" organisations and force the new Palestinian government to recognise past deals with Israel.