The United Nations agency for Palestinian refugees will cut more than 260 jobs and curtail mental health services and mobile health clinics, it announced on Wednesday, the first reduction since the United States suspended tens of millions of dollars in funding this year.

“These cuts are unprecedented in their scope and depth and their consequences are likely to be dramatic, widespread and unpredictable,” Christopher Gunness, the agency’s spokesman, said in an email.

The cuts are the first outcome of a significant American reduction in contributions to the United Nations Relief and Works Agency, or Unrwa. The Trump administration has provided about $60 million this year. That reflects a drop of more than 80 percent from the $360 million the United States contributed in 2017.

Historically, the United States has been one of the biggest donors to Unrwa, which provides food, education, health services and employment to many Palestinians classified as refugees in Gaza, East Jerusalem, the West Bank, Jordan, Lebanon and Syria.