UPDATE 1-Romney says would exert U.S. leadership globally

* Bolstering U.S. ties with Israel

* Would build up Navy

* Strengthen cooperation with Mexico

By Steve Holland

CHARLESTON, S.C., Oct 6 (Reuters) - Republican presidential candidate Mitt Romney will vow on Friday to exert U.S. leadership worldwide with military power and diplomacy in a speech aimed at showing he has foreign policy mettle.

Romney will say that if elected in November 2012, he will promise a series of actions over his first 100 days in office to demonstrate American might.

"I will not surrender America's role in the world. This is very simple: If you do not want America to be the strongest nation on Earth, I am not your president," Romney will say, according to excerpts released by his campaign.

Romney, a former businessman who was also Massachusetts governor, has little foreign policy experience. In his speech, he seeks to demonstrate to Americans he would be able to handle crises abroad and exert U.S. leadership in an unsettled world.

He also attempts to portray Democratic President Barack Obama, whom he wants to replace, as weak despite some clear foreign policy successes by the president, such as the killing last May of al Qaeda leader Osama bin Laden and well-received efforts to wind down the U.S. troop presence in Iraq and Afghanistan.

Romney would step up pressure on Iran over its nuclear program by ordering the regular presence of an aircraft carrier task force in both the eastern Mediterranean and the Gulf region and begin discussions with Israel to increase military and intelligence coordination.

MAINTAINING MILITARY SUPREMACY

Stressing the need to maintain U.S. military supremacy, Romney will pledge to prevent any massive cuts in defense spending. He has denounced an August agreement between Obama and Congress that could permit deep cuts in the U.S. defense budget as part of an effort to tackle record budget deficits.

Romney would order the U.S. Navy built up by increasing the shipbuilding rate to about 15 a year from nine in order to bolster the American presence on the high seas.

"The United States should always retain military supremacy to deter would-be aggressors and to defend our allies and ourselves," he will say.

He would work to bolster relations with Israel that some critics say have been damaged by what they feel was Obama's favoring of the Palestinians over Israel.

Romney would also strengthen the U.S.-British "special relationship" and begin talks with Mexico on border violence due to the drug trade.

"America must lead the world, or someone else will," Romney will say.

Romney is hoping South Carolina will give him a second chance in 2012.

Consigned to a humbling fourth-place finish in the South Carolina Republican primary in 2008, Romney has some convincing to do to persuade the state's conservatives to back him this time over rivals such as Texas Governor Rick Perry.

Romney on Thursday spent the first of two days in the Charleston area trying to appeal to U.S. military veterans who live in the state and are an influential voting bloc.

He leads in national opinion polls over Perry and businessman Herman Cain three months before Republican primary voting begins, but is attempting to break out of the pack.