Wisconsin Gov. Scott Walker Wouldn't Rule Out Re-Invasion of Iraq He would consider re-invasion if it were necessary to protect U.S. interests.

 -- Wisconsin Gov. Scott Walker says he wouldn’t rule out a full-blown re-invasion of Iraq if he were to become the next commander-in-chief.

"It would not be limited to anything out there," Walker told ABC's Jonathan Karl in an exclusive interview with for “This Week.” "Once we start saying how far we're willing to go or how many troops we're willing to invest, we send a horrible message, particularly to foes in the Middle East who are willing to wait us out."

Walker has been critical of President Obama’s handling of Iraq and Syria for its limited scope but also qualified that he does not believe in “open-ended, limitless engagements.” Though he has been sparse in offering specific changes to U.S. policy in the fight against ISIS, the likely presidential candidate said he has been deepening his understanding of international affairs in recent months.

“My belief is if I’m gonna, I'm even thinking about running for president of the United States, it's not about preparing for debates,” he said. "It's about being prepared to be the president of the United States."

The governor said he has had discussions in recent months with British Prime Minister David Cameron, former Secretaries of State Henry Kissinger and George Schultz and military leaders. He name-dropped U.S. generals Hayden, Mattis, Keane, “and others like that.”

“You gotta be ready on January 20th of 2017,” he said.

Obama, who has largely refrained from directly engaging the Republican contenders by name, recently took a swipe at Walker, saying he needs to “bone up” on his foreign policy credentials.

“I thought it was interesting for the president to say that -- the guy who called ISIS the JV squad and Yemen a success story somehow suggesting someone else should bone up on foreign policy,” Walker said.

In April, the president scoffed at Walker for saying that he would scrap a nuclear deal with Iran on his first day in the White House.

"It would be a foolish approach to take," Obama told NPR at the time. "Perhaps Mr. Walker, after he's taken some time to bone up on foreign policy, will feel the same way."

While Walker indicated he has been doing his homework, foreign policy has been an early weak spot for the Wisconsin governor in testing the waters of a presidential bid.

Earlier this year, he referred to Ronald Reagan’s firing of air traffic controllers in a 1971 strike the “most significant foreign policy decision of my lifetime” and also suggested that his experience battling union protesters in Wisconsin has helped prepare him to take on ISIS fighters in vying to become the next commander-in-chief.

Same-Sex Marriage

With the Supreme Court poised to rule on state bans to same-sex marriage, Walker said he would be open to the idea of a constitutional amendment to define marriage as between one man and one woman -- a process that he emphasized would have to originate from the states.

“If the court decides that, the only next approach is for those who are supporters of marriage being defined as between one man and one woman is ultimately to consider pursuing a constitutional amendment,” he said.

Praise for Rubio

Walker, who has in the past said the presidential nominee should be a governor, said a nominee with executive experience continues to be his preference “because governors don’t just talk and give speeches.” But he made an exception for Florida Sen. Marco Rubio.

“Someone like Marco Rubio I have real confidence in,” Walker said. “I think he’s got a great background. He and I agree on many issues, particularly on foreign policy and a strong national defense and I have great admiration for him.”

Record on Jobs

Walker defended his record on job creation in Wisconsin, despite falling short on a promise to create 250,000 jobs in the state -- a goal he fell short of by almost 50 percent.

“We set a big, bold goal,” Walker acknowledged, before touting an unemployment rate that stands below the national average at 4.4 percent and a list of other promises kept.

“Look at all the other promises we made,” Walker said. “Four years in a row, property taxes are lower than when we started, the next two years they'll be out there. We froze tuition, we fixed the budget from $3.6 billion in a hole to a surplus. The rainy day fund is 165 times bigger than when we took office. Schools are better. You look at one promise after another. We fulfilled it.”