The Rafah border crossing into Gaza was closed on Wednesday due to an unspecified "security circumstance" but U.S. officials were working with Egypt and Israel to get it reopened, U.S. State Department deputy spokesperson Vedant Patel said.

Rafah, which is controlled by Egypt and does not border Israel, is the only point of aid delivery since Israel launched a military assault and siege of Gaza in retaliation for an attack by Hamas militants from the coastal strip on Oct. 7.

Evacuations of foreign passport holders through the crossing were suspended on Saturday and Sunday after an Israeli strike on an ambulance that was heading to Rafah, but the crossing was open again on Monday and Tuesday.

"Our understanding is that given a security circumstance the Rafah border crossing remains closed today," Patel said during a regular press briefing.

The United States expects the Egypt-controlled crossing will be reopened at "regular intervals" so that aid can enter the Gaza Strip and foreign nationals can continue to depart, Patel said.

More than 400 U.S. citizens, family members and permanent residents have so far exited Gaza since foreign passport-holders began leaving via Rafah last week, he added.

"This is an incredibly fluid situation. The border crossing has opened on many instances and allowed for the safe ... exit for foreign nationals who have sought it," he said.

Washington has urged Israel to agree to humanitarian pauses so that aid can flow into Gaza.

Patel said 81 trucks carrying food, medicine, health supplies, bottled water and hygiene products crossed into the strip on Tuesday, bringing to about 650 the total number of trucks that have crossed since a diplomatic agreement was reached to reopen the crossing on Oct. 21.