GAZA/DOHA/WASHINGTON, Jan 30 (Reuters) - The United States vowed to take "all necessary actions" to defend American forces after a drone attack killed three U.S. troops in Jordan, while Qatar said it hoped U.S. retaliation would not damage regional security or undercut progress toward a new Gaza hostage-release deal.

Sunday's attack by Iran-backed militants was the first deadly strike against U.S. troops since the Israel-Hamas war erupted in October and marks a major escalation in tensions that have engulfed the Middle East.

White House National Security spokesman John Kirby said on Monday the United States did not want a wider war with Iran or in the region, "but we got to do what we have to do."

Iran has denied any role. Biden has previously ordered retaliatory attacks on Iran-backed groups but has so far stopped short of hitting Iran directly.

"Have no doubt - we will hold all those responsible to account at a time and in a manner of our choosing," Biden said on Sunday, while Austin said at the Pentagon on Monday:

"The president and I will not tolerate attacks on U.S. forces and we will take all necessary actions to defend the U.S. and our troops."

In Gaza, Israel launched an assault on the Hamas-ruled enclave's biggest city. Residents of Gaza City said air strikes killed and wounded many people, while tanks shelled eastern areas and naval vessels fired at western beachfront areas.

Israel said late last year it had largely completed operations in northern Gaza and has recently aimed the brunt of its might at southern Gaza. The renewed push in Gaza City, where residents reported fierce gun battles near the main Al-Shifa Hospital, suggested that the war was not going to plan.

Biden's administration is under pressure to respond to the drone attack firmly without triggering a wider war. It has also been trying to facilitate the release by Hamas, which rules Gaza, of more than 100 hostages seized by the militants in their deadly Oct. 7 rampage into southern Israel.

Qatari Prime Minister Sheikh Mohammed bin Abdulrahman bin Jassim al Thani told a Washington think tank he hoped U.S. retaliation would not undercut progress toward a new hostage release deal in talks last weekend.

He said potential U.S. retaliation "will definitely have an impact on regional security and we hope things get contained."

CIA Director William Burns met Sheikh Mohammed, as well as the head of Israel's Mossad intelligence service and the head of Egyptian intelligence, on Sunday in Paris for talks described as constructive by Israel, Qatar and the U.S., albeit with significant gaps remaining.

U.S. Secretary of State Antony Blinken said the Paris talks raised hope that a Qatar-mediated negotiating process could resume. Before collapsing, the mechanism led to a week-long ceasefire agreement in November when Hamas freed around 100 hostages.

A framework for a possible second deal developed in Paris "is a strong one and a compelling one that ... offers hope that we can get back into this process," he said at a news conference with NATO Secretary General Jens Stoltenberg.

"Hamas will have to make its own decisions," said Blinken, who declined to reveal details of the proposal.

Photo from Reuters