Mitt Romney joined a list of mostly Republican leaders Monday calling for a special independent prosecutor to investigate leaks about U.S. counterterrorism programs, saying sensitive information "should not be leaked in a way that puts American interests and our people in jeopardy."

"I do think that a special prosecutor should look into them," Romney told Fox News Channel's Carl Cameron. "I think we should make every effort to understand how those matters that relate to the safety of our men and women in uniform around the world and to our foreign policy plans."

The New York Times and Newsweek ran reports revealing a "kill list" of terrorist targets, as well as details about a cyber-warfare campaign against Iran and the U.S. drone program.

Sen. John McCain (R-Ariz.) has called for an independent investigation, as have other Senators including Lindsey Graham (R-S.C.) and Sen. Joseph Lieberman (I-Conn.).

In today's interview, Romney wouldn't give any hints as to when he may pick a running mate. And even though Rep. Paul Ryan (R-Wisc.) joined him on the campaign trail today he would only say, "There are a number of terrific people in our party who could potentially serve as a vice president. We are going through that process now of making that decision, but I got no names for you."

He wouldn't confirm or deny reports that he may choose a running mate early, before the Republican convention, just saying it's something "I'll be deciding down the road."

"I don't know what the history is of all the people who have been selected and when they've been nominated or decided upon by the various candidates," Romney said in Wisconsin. "No timetable for you now, but I'll decide exactly when it is I'll name my V.P. It could be at the convention, it could be earlier. Probably not much later than the convention, but I expect it will come when it comes."

As he had Sunday on CBS News' Face the Nation, the presumptive GOP nominee twice refused to say whether he would repeal the president's order on immigration. Cameron asked why he wouldnt say he would reverse it, as he does consistently with the president's health care plan, Romney answered he favors a "long term solution," without going into detail. He did say it's an issue he will start working on "as soon as I get elected" so he's "ready to go immediately."

"When we talk about illegal immigration I think I want to start by saying we got to secure the border, we've got to have an employment verification system," Romney said. "And then with regards to these children who came in here brought by their parents who came here illegally, how we deal with this is something that I think deserves a long term solution, and I don't think we go jumping from one solution to the other. I think the president made a mistake by putting out there what he called a stopgap measure. I don't think that's the right way to go."

President Obama announced Friday that illegal immigrants will no longer face the threat of deportation if they were brought to the U.S. before they turned 16, are younger than 30, have no criminal record and have graduated from high school or earned a G.E.D. It could affect 800,000 people in this country.

Romney called the president's announcement "partly political" and said it wasn't the role of "a nominee like myself go out and talk about short term answers."

"I want to put in place a long term solution to our illegal immigration challenges and make sure those people who have come here illegally understand what their status will be," Romney said.

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