"This country's made a lot of mistakes and the war in Iraq was one of them," Trump told ABC's This Week.
"There were no weapons of mass destruction. There were no anything," he said.
"We got into a war, we have destabilised the entire Middle East," he said, alleging that the US President, Barack Obama, got America out of the war the wrong way.
Trump said in 2003-2004, he was the only one on the stage who said don't go into Iraq; as this would destabilise the Middle East.
Also Read
"I was against the war even though I am the most militaristic person there is. I said, if you do this war, you're going to destabilise the entire Middle East. That's exactly what happened. That's why we have the migration and all of the other problems that we have right now in the Middle East," Trump said.
"In this campaign and the last few weeks, he has kind of developed a disturbing pattern of telling things that simply aren't true. Just this week alone, he had an ad pulled off the air because it lied about sanctuary cities and immigration," Rubio told Fox news.
"He has also lied about my position on marriage, my position on Planned Parenthood. We also saw what he did to Ben Carson," he said.
"These were paid robocalls that were being made out to his activists in Iowa, telling them to inform people at the caucus site that Ben Carson dropped out. Donald Trump made an allegation last night, I don't know if it's true or not, about those sorts of robocalls happening here now," Rubio alleged.
"He stands on the Senate floor; he's got no support from one senator. You look at his colleagues, he has absolutely no endorsements. He's a lone wolf and he's going to get nothing done. He's not a leader," he said.
"Cruz never employed anybody, never created a job. This is the wrong guy... He is a nasty guy, no matter how you figure it," Trump alleged.
"He holds up the Bible and, believe me, he might hold up the Bible but this is not a man that, in my opinion, should be President. I think he's really done a great disservice to himself and to the Republican Party," Trump said.