Senator Lindsey Graham to announce presidential bid next month
Republican Senator Lindsey Graham, pictured here in Washington, DC on March 12, 2015, has accused Obama of softening America's power in the Middle East (AFP Photo/Mandel Ngan)

U.S. Senator Lindsey Graham of South Carolina, a longtime Washington insider and critic of President Barack Obama's foreign policy, said he would announce on June 1 whether he will seek the 2016 Republican presidential nomination.

"I'm running because I think the world is falling apart," Graham said on Monday in an interview on CBS, all but declaring his official candidacy. He has previously said he was "99.9 percent" sure he would run.

Graham is a foreign policy hawk who is often aligned with Republican Senator John McCain of Arizona, one of his best friends. In January, Graham said he was exploring running for president and saw the battle against Islamic extremism as a top priority.

Graham would join a crowded Republican field if he formally enters the race and would need to boost his visibility before the first debate in Cleveland in August. He said he plans to make his announcement in central South Carolina, the state he has represented in Congress since 1995.

At an event in Iowa on Saturday, Graham said Obama is to blame for the rise of Islamic State militants in Iraq because he failed to leave a sufficient post-war contingent of U.S. troops there.

On Monday, he told CBS that knowing what he does now, he would not have launched a ground invasion of Iraq as former President George W. Bush did. But Graham said then-Iraqi leader Saddam Hussein needed to be removed somehow.

"He needed to go. But if I knew the intelligence was faulty, I'd have reconfigured," Graham said. He said he was considering running not because other candidates lacked foreign policy chops but because he thought he would make a good commander-in-chief.

Republican presidential candidates have been drawn into a debate over the Iraq war after former Florida Governor Jeb Bush, who is the ex-president's brother, gave several wobbly answers to questions about how he would have handled the situation.