WASHINGTON (AP) — The Biden administration is expected to announce soon that the U.S. government will begin operating evacuation flights to help Americans leave Israel as Israel prepares to escalate retaliatory action against Hamas militants in the Gaza Strip, according to two people familiar with the plans.

The evacuation flights are expected to begin operating as early as Friday, according to the people, who requested anonymity to discuss the plans before the official announcement.

The U.S. government is arranging for at least four charter flights a day out of Israel through Frankfurt, Germany.

There are still some commercial carriers flying in and out of Tel Aviv’s Ben Gurion airport, and ground routes are open to leave Israel. White House officials, however, have voiced concern that those options may not be feasible or affordable for some Americans in Israel who want to leave.

White House National Security Council spokesman John Kirby said on Wednesday that the administration was exploring “a range of options” for assisting Americans who want to leave.

The White House has said a “handful” of Americans are among the dozens of people that Hamas took hostage.

U.S. Secretary of State Antony Blinken visited Israel on Thursday to meet with Israeli Prime Minister Benjamin Netanyahu and Israeli citizens. He was joined by the deputy special representative for hostage affairs, Steve Gillen, who will stay in Israel to to support the efforts to free the hostages.

Blinken said Thursday that Americans would continue pushing regional countries for a safe passage in and out of Gaza, which could help the hundreds of American civilians trapped in the blockaded enclave during the fighting.