The United States warned against any "escalation" in the Middle East in the wake of Israel's war with Hamas, Defense Secretary Lloyd Austin said Sunday, hours after the Pentagon moved to step up military readiness in the region.

The United States has seen a "prospect of a significant escalation of attacks on our troops" in the region, Austin said Sunday, adding that the US military was preparing for "the ability to respond."

"If any group or any country is looking to widen this conflict and take advantage of this very unfortunate situation that we see, our advice is: don't," he told ABC News.

"We maintain the right to defend ourselves and we won't hesitate to take the appropriate action," he added.

His comments came hours after the Pentagon said it was upping readiness in the region in response to "recent escalations by Iran and its proxy forces."

Austin ordered the activation of air defense systems and notified additional forces that they may be deployed soon.

Austin did not say how many US troops would be added to those already in the region.

The Pentagon's moves came after what Austin had earlier described in a statement as "detailed discussions" with President Joe Biden.

"These steps will bolster regional deterrence efforts, increase force protection for US forces in the region, and assist in the defense of Israel," Austin said.

The steps continued the Biden administration's response since Hamas militants in the Gaza Strip stormed Israel on October 7, taking more than 200 hostages and killing at least 1,400 people, according to Israeli officials.

tensions rising

Israel has since vowed to destroy Hamas, and says around 1,500 of the group's fighters were killed in clashes before its army regained control of the area initially under attack.

Austin said he had activated deployment of a Terminal High Altitude Area Defense (THAAD) battery and additional Patriot battalions "throughout the region."

"Finally, I have placed an additional number of forces on prepare-to-deploy orders as part of prudent contingency planning, to increase their readiness and ability to quickly respond as required," Austin said.

Tensions are rising along Israel's northern border with Lebanon after the Israeli army traded fire with the Iran-backed militant group Hezbollah amid fears of a new front opening as Israel battles Hamas.

In south Lebanon on Saturday, Hezbollah said four of its fighters were killed. Palestinian militant group Islamic Jihad said one of its fighters was also killed.

Armed factions close to Iran have threatened to attack US interests in Iraq over Washington's support for Israel.

Multiple Iraqi bases used by US-led coalition troops have been targeted in several attacks in recent days.

Israel's military said Saturday it would intensify strikes on Hamas-controlled Gaza ahead of a planned ground invasion.

The military has pounded Gaza with relentless strikes in response to Hamas's 7 October attack.

The bombing campaign has killed more than 4,650 Palestinians, mainly civilians, according to the Hamas-run health ministry, and reduced swaths of the densely populated territory to ruins.

A first trickle of aid entered the Palestinian enclave from Egypt on Saturday, but the 20 trucks permitted to cross have been described as a "drop in the ocean" given the needs of 2.4 million residents.