"We are concerned at the possibility of Iranian proxies escalating their attacks against our own personnel, our own people," Secretary of State Antony Blinken said on CBS News. "We expect there is a likelihood of escalation."
"No one should take advantage of this moment to escalate to further attacks on Israel or, for that matter, attacks on us on our personnel."
Blinken said the United States, which has sent two carrier groups to the eastern Mediterranean, was "taking every measure to make sure that we can defend them. And if necessary, respond decisively."
Blinken's words echoed — and served to reinforce — an earlier message from Defense Secretary Lloyd Austin, who warned of a "prospect of significant escalation of attacks on our troops" in the region.
The comments from the two most senior members of President Joe Biden's cabinet came amid growing fears that pro-Iranian Hezbollah militants in southern Lebanon, or other groups supported by Tehran, might join in the war.
Speaking on ABC News, Austin sent a stern warning to Iran and allied militant groups.
"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 said.
"We maintain the right to defend ourselves and we won't hesitate to take the appropriate action."
Austin ordered the activation of air defense systems and notified additional forces that they may be deployed soon.
Austin did not say how many U.S. troops would be added to those already in the region.
The Pentagon's moves to boost troops strength in the region came after what Austin had earlier described in a statement as "detailed discussions" with 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 Oct. 7, taking more than 200 hostages and killing at least 1,400 people, according to Israeli officials.
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 in southern Israel targeted in initial attack.
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 second front opening as Israel battles Hamas.
Armed groups allied with Iran have threatened to attack U.S. interests in Iraq over Washington's support for Israel. Multiple Iraqi bases used by U.S.-led coalition troops have been targeted in several attacks in recent days.
Israel's military said it would intensify strikes on Hamas-controlled Gaza ahead of an expected ground invasion.
The Israeli military has pounded Gaza with relentless strikes in response to Hamas's Oct. 7 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.
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