WASHINGTON, Oct 15 (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.

Photo from Reuters