• Trump says it has been difficult to make a deal with Iran
• US fully expects Iran to retaliate, official says
• A sustained campaign carries more risk to US forces, broader Middle East

WASHINGTON, Feb 13 (Reuters) - The U.S. military is preparing for the possibility of sustained, weeks-long operations against Iran if President Donald Trump orders an attack, two U.S. officials told Reuters, in what could become a far more serious conflict than previously seen between the countries.

The disclosure by the officials, who spoke on condition of anonymity due to the sensitive nature of the planning, raises the stakes for the diplomacy underway between the United States and Iran.

U.S. and Iranian diplomats held talks in Oman last week in an effort to revive diplomacy over Tehran’s nuclear program, after Trump amassed military forces in the region, raising fears of new military action.

U.S. officials said on Friday the Pentagon was sending an additional aircraft carrier to the Middle East, adding thousands more troops along with fighter aircraft, guided-missile destroyers and other firepower capable of waging attacks and defending against them.

Trump, speaking to U.S. troops on Friday at a base in North Carolina, said it had “been difficult to make a deal” with Iran.

“Sometimes you have to have fear. That’s the only thing that really will get the situation taken care of,” Trump said.