By Michelle Nichols

UNITED NATIONS (Reuters) - The United Nations said on Thursday it will not take part in a U.S.-backed humanitarian operation in Gaza because it is not impartial, neutral or independent, while Israel pledged to facilitate the effort without being involved in aid deliveries.

"This particular distribution plan does not accord with our basic principles, including those of impartiality, neutrality, independence, and we will not be participating in this," deputy U.N. spokesperson Farhan Haq told reporters on Thursday.

The U.S.-backed Gaza Humanitarian Foundation will start work in Gaza by the end of May under a heavily-criticized distribution plan, but has asked Israel to let the United Nations and others resume deliveries now until it is set up.

The foundation has also asked Israel to expand an initial limited number of so-called secure aid distribution sites in Gaza's south to the enclave's north within 30 days.

"I'm not familiar with those requests, maybe when they went into Jerusalem, but I will tell you that we appreciate the effort of the United States," Israel's U.N. Ambassador Danny Danon told reporters on Thursday.

"We will not fund those efforts. We will facilitate them. We will enable them," he said. "Some of them will have to cross through territory that we operate."

No humanitarian assistance has been delivered to Gaza since March 2, and a global hunger monitor has warned that half a million people face starvation - a quarter of the population in the enclave where Israel and Palestinian militant group Hamas have been at war since October 2023.

Israel has accused Hamas of stealing aid, which the group denies, and is blocking humanitarian deliveries to Gaza until Hamas releases all remaining hostages.

Israel and the U.S. have urged the U.N. and aid groups to cooperate with the GHF. However, they have raised concerns that the operation would not stick to the humanitarian principles of humanity, impartiality, independence and neutrality.

Danon said the "major operation" will start very soon.

"Israel will not be involved inside the operation center. We will not be the one giving the aid. We will not be even in those centers. It will be run by the fund itself, led by the U.S. And I'm happy that few NGOs joined these efforts," Danon said.

(Reporting by Michelle Nichols; editing by Susan Heavey ansd Ed Osmond)