The U.S. military launched an air assault on dozens of sites in Iraq and Syria used by Iranian-backed militias Friday, in the opening salvo of retaliation for the drone strike that killed three U.S. troops in Jordan last weekend, officials told The Associated Press.

President Joe Biden and other top U.S. leaders have been warning for days that the U.S. would strike back at the militias, and they made it clear that it wouldn't be just one hit, but would be a "tiered response" over time. The officials spoke on condition of anonymity to discuss military operations not yet made public.

Three pro-Iran fighters were killed in Israeli strikes south of Damascus Friday, a war monitor said, with Iranian media reporting an adviser from the Revolutionary Guards was among the dead.

The Syrian Observatory for Human Rights said "three members of pro-Iran groups, including an Iranian and an Iraqi" were killed in "Israeli air strikes".

Iraq's pro-Iran Al-Nujaba movement said Friday it intends to press on with attacks on U.S. troops in the Middle East, despite Washington's threat to hit back after three of its soldiers were killed in Jordan.

"Any (U.S.) strike will result in an appropriate response," Al-Nujaba leader Akram al-Kaabi said in a statement, adding the group would continue its actions until its demands are met for U.S. troops to leave Iraq and an end to Israel's war on Hamas in Gaza.

Defense Secretary Lloyd Austin has said it's time to further disable Iran-backed militias that have struck at U.S. forces and ships in the Middle East and the U.S. is preparing to take significant action in response to the deaths of three U.S. service members in Jordan.

For days the U.S. has hinted strikes are imminent. While the threat of retaliation for Sunday's deaths has driven some militant groups to say they were stopping hostilities, as late as Thursday Yemen's Houthi rebels were still attacking vessels and fired a ballistic missile at a Liberian-flagged container ship in the Red Sea.

President Joe Biden on Thursday issued an executive order that targets Israeli settlers in the West Bank who have been accused of attacking Palestinians and Israeli peace activists in the occupied territory, imposing financial sanctions and visa bans in an initial round against four individuals.

Those settlers were involved in acts of violence, as well as threats and attempts to destroy or seize Palestinian property, according to the order. The penalties aim to block the four from using the U.S. financial system and bar American citizens from dealing with them. U.S. officials said they were evaluating whether to punish others involved in attacks that have intensified during the Israel-Hamas war.

Satellite photos show new demolition along a 1-kilometer-deep path on the Gaza Strip's border with Israel, according an analysis by The Associated Press and expert reports. The destruction comes as Israel has said it wants to establish a buffer zone there, over international objections, further tearing away at land the Palestinians want for a state.

The demolition along the path represents only a sliver of the wider damage from the Israel-Hamas war seen in Gaza, which one assessment suggests has damaged or destroyed half of all the buildings within the coastal enclave.

Hamas has given its "initial" approval to a planned humanitarian pause in its war with Israel and a hostage-prisoner exchange, Qatar said Thursday, as fighting raged in the Gaza Strip.

However, a source close to Hamas told AFP there was no agreement yet on the proposal.

Britain's top diplomat has said that his country could officially recognize a Palestinian state after a cease-fire in Gaza without waiting for the outcome of what could be yearslong talks between Israel and the Palestinians on a two-state solution.

Foreign Secretary David Cameron, speaking to The Associated Press during a visit Thursday to Lebanon intended to tamp down regional tensions, said no recognition could come while Hamas remained in Gaza, but that it could take place while Israeli negotiations with Palestinian leaders were continuing.

Israeli-made Pegasus spyware was used in Jordan to hack the cellphones of at least 30 people, including journalists, lawyers, human rights and political activists, the digital rights group Access Now said Thursday.

The hacking with spyware made by Israel's NSO Group occurred from early 2020 until last November, Access Now said in its report. It did not accuse Jordan's government of the hacking.

A new explosion was reported off Yemen on Thursday after overnight U.S. strikes targeted 10 attack drones and a ground control station belonging to the Iran-backed Houthi rebels.

The explosion, reported by the United Kingdom Maritime Trade Operations agency, happened near a vessel west of the port city of Hodeida.