WASHINGTON - The United States is "deeply troubled" by the adoption of legislation in Israel that would ban the operation of a UN agency for Palestinian refugees, State Department Spokesperson Matthew Miller said Tuesday.

Miller said the legislation, passed Monday but yet to be implemented, "poses risks for millions of Palestinians" who rely on the United Nations Relief and Works Agency for Palestinian Refugees in the Near East (UNRWA) for essential services such as healthcare and education.

The spokesperson said UNRWA's role -- while critical not only in Gaza, but also in the West Bank and the broader Middle East region -- "cannot be filled by anyone else" right now in terms of "delivering food, water and other humanitarian assistance to civilians in Gaza".

Reiterating the point US secretaries of state and defense made in a recent letter to their Israeli counterparts, Miller said should Israel implement the bill, "there could be consequences under US law and US policy."

"We are going to engage with the government of Israel in the days ahead about how they plan to implement it. We're going to watch and see if there are legal challenges to the law and if there's any impact by those legal challenges, and then we will make our decisions after looking at all those factors," Miller said.