The already tense relationship between the U.S. and the Palestinians deteriorated further on Saturday, with the latter threatening to cut off all communication with the Trump administration over plans to close the Palestine Liberation Organization office in Washington, D.C.

The plan to close the office is “very unfortunate and unacceptable,” Palestinian negotiator Saeb Erekat said.

Earlier Saturday, the U.S. State Department said the office will close after the Palestinians called for Israelis to be prosecuted by the International Criminal Court for alleged crimes committed against Palestinians.

Officials on Friday said the office could stay open only if President Trump found within 90 days that the Palestinians were serious about peace talks with Israel. Trump had been adamant about successful peace talks between the two sides during both his campaign and since taking office.

It is not immediately clear if the Palestinians must leave the office completely, or close it to the public. It is also unclear when the office will close.

Erekat accused the U.S. of buckling under pressure from Israel Prime Minister Benjamin Netanyahu, and added that the Palestinians are “trying to cooperate to achieve the ultimate deal.”

Netanyahu’s office said closing the office is a “matter of U.S. law.”