Washington CNN  — 

Sen. Lindsey Graham said Monday that the Iraq War was not a mistake, even though he was less certain whether he agreed with the ground invasion authorized by President George W. Bush in 2003.

Graham was the latest presidential hopeful to tangle with the thorny hypothetical posed to many in the burgeoning Republican field over the past week: Would they have ordered the invasion of Iraq knowing that the nation did not have weapons of mass destruction?

“If I knew then what I know now, a land invasion may not have been the right answer,” Graham told CNN’s Wolf Blitzer on “The Situation Room,” detailing the record of abuse and rogue behavior by Saddam Hussein. “He had a lot to do with destabilizing the region.”

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Graham later said he would have “kept the pressure to get rid of Saddam,” though he did not detail what that would mean.

“At the end of the day, I blame President Obama for the mess in Iraq and Syria, not President Bush,” Graham said.

Graham criticized Obama for not keeping a residual security presence in Iraq after troops left the country in 2011. If he was elected president, Graham said he would increase the number of boots on the ground from 3,000 to about 10,000 in order to stymie the growing threat posed by the Islamic militant group, ISIS.

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“The longer (ISIS) is allowed to survive in Iraq and Syria, the more likely they are to attack us here at home,” Graham said, acknowledging more troops would mean more American casualties.

“I think 10,000 troops would allow us to train the Iraqi army at a faster pace, give them capability that they don’t have,” he said.

“It will take us thousands of American soldiers over there to protect millions of us back here at home,” the South Carolina Republican added.

Graham said Monday morning that he will announce whether he will run for president on June 1 in South Carolina, which will host the third nominating contest of 2016.