By Nandita Bose, Humeyra Pamuk and Steve Holland

WASHINGTON/CAIRO (Reuters) – The United States is bolstering its firepower in the Middle East to prevent the spread of the conflict between Israel and Palestinian militant group Hamas and deter Iran from getting involved as international fears of a wider regional war grow.

The newest U.S. aircraft carrier – and the world’s largest – is already in the eastern Mediterranean and set to be joined by a second U.S. aircraft carrier in the next 10 days.

While the White House says there are “no plans or intentions” for their use, it means U.S. military assets would be in place to provide air support to protect U.S. national security interests if needed. The U.S. also has an array of bases in the Middle East with troops, fighter aircraft and warships.

“Every effort is being made to stop this from becoming a regional conflict. If that happens, it is going to draw U.S. resources in a big way,” said a U.S. official, speaking on condition of anonymity. “I don’t want to speculate on what assistance can be offered if there is a wider conflict, those decisions haven’t been made yet.”

U.S. Secretary of State Antony Blinken – speaking in Cairo on Sunday after days of Middle East shuttle diplomacy – delivered a blunt message and a veiled warning to U.S. foe Iran: “When it comes to Israel security, we have Israel’s back.”

He said the deployment of two aircraft carrier strike groups was “not to provoke anyone, but just to send a very clear message of deterrence that no one should do anything that widens this conflict in any way, or that furthers aggression against Israel from any other direction.”

Iranian Foreign Minister Hossein Amirabdollahian warned on Sunday that “the hands of all parties in the region are on the trigger,” while Iran’s mission to the United Nations in New York said if Israel does not attack it, its interests or citizens, then Iran’s armed forces would not engage militarily.

Israel has vowed to annihilate Iran-backed Hamas – which controls the Gaza Strip – after its fighters stormed Israeli towns eight days ago, killing 1,300 people and seizing hostages in the worst attack on civilians in the country’s history.

HEZBOLLAH FEARS

International diplomacy has been focused on preventing a spill over of the conflict – particularly into Lebanon.

While Israel has been intensely bombing Gaza for the past week and preparing for a ground offensive, the country’s military has also clashed on the Lebanese border with the Iran-backed, heavily armed Hezbollah group in the deadliest confrontations since they fought a month-long war in 2006.

When asked if the United States could provide air support in northern Israel, White House national security spokesperson John Kirby (NYSE:) said: “No plans or intentions at this time.”

“That said, we take our national security interests seriously and we have ample military force in the region to protect and defend those interests as needed,” Kirby added.

Any decision to launch military action in the Middle East would come from U.S. President Joe Biden, a Democract, himself. Such a move already has some Republican support.

Senator Lindsey Graham, an influential Republican voice on national security affairs, told Reuters on Sunday he would propose that Congress authorize a U.S. attack on Iran’s oil industry if “a second front is opened in the north” of Israel.

“If there’s an effort by Hezbolllah to unleash a massive attack on Israel, the Iranians should pay a heavy price for that,” he said. “Any escalation by Iran – triggering Hezbollah, killing the hostages – should put them in the crosshairs.”

U.S. Defense Secretary Lloyd Austin said on Thursday the United States had seen no indications that Lebanon’s Hezbollah militants were amassing to potentially attack Israel, widening the conflict.

“We’ve not seen any massing of forces along the border,” Austin said. “This is something that the Israelis are focused on. We are also looking for additional things that could widen the conflict here and hopefully, we won’t see those things.”

Two U.S. officials, speaking on the condition of anonymity, said the naval ships in the region were truly meant as a show of force and to give Biden options in the future if needed, rather than some certain plan for the U.S. to get involved.