WASHINGTON (Reuters) - The United States will not provide $45 million in food aid for Palestinians that it pledged last month as part of the West Bank/Gaza Emergency Appeal led by the U.N. Relief and Works Agency (UNRWA), the U.S. State Department said on Thursday.

The State Department had said on Tuesday that Washington would withhold a separate $65 million it had planned to pay the U.N. agency that serves the Palestinians, saying UNRWA needed to make unspecified reforms.

State Department spokeswoman Heather Nauert denied the withholding of the $65 million was to punish Palestinians, who have been sharply critical of Trump's announcement last month that he would move the U.S. Embassy to Jerusalem from Tel Aviv.

In a Dec. 15 letter to UNRWA Commissioner-General Pierre Krähenbühl, State Department Comptroller Eric Hembree had pledged $45 million to the West Bank/Gaza Emergency Appeal.

"The United States plans to make this funding available to UNRWA in early 2018," according to the letter, seen by Reuters on Thursday. "An additional letter and contribution package confirming this contribution will be sent by or before early January 2018."

The United States had made clear to UNRWA that the $45 million was a pledge aimed at helping the agency with "forecasting," but it was not a guarantee, Nauert told reporters at a regular State Department briefing.

"At this time, we will not be providing that, but that does not mean - I want to make it clear - that does not mean that it will not be provided in the future," Nauert said.

She repeated the U.S. view that UNRWA needs reform, saying there are a lot more refugees in the program than previously, and that "money coming in from other countries needs to increase as well to continue paying for all those refugees."

"So we're asking countries to do more," Nauert said. "Fundamentally, we just don't believe that we have to be the chief donor to every organization around the world."

Despite the decision on the food aid pledge, she said: "We are the most generous country on the planet. We continue to be."

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Trump said in a Twitter post on Jan. 2 that the United States gives the Palestinians hundreds of millions of dollars a year, "but get no appreciation or respect."

The decisions to curb funding are likely to compound the difficulty of reviving Israeli-Palestinian peace talks as well as further undermine Arabs' faith that the United States can act as an impartial arbitrator.

The last talks collapsed in 2014, partly due to Israel's opposition to an attempted unity pact between the Palestinian factions Fatah and Hamas, and because of Israeli settlement building on occupied land that Palestinians seek for a state, among other factors.

(Reporting by David Alexander and Arshad Mohammed; Additional reporting by Michelle Nichols at the United Nations; Writing by David Alexander; Editing by Daniel Wallis)