The former Massachusetts governor told New Hampshire voters Monday night that Pakistan is playing both sides -- going after the Taliban within its borders in some cases and helping it in others. That's unacceptable, he said.
"It's pretty straightforward to say, `Listen guys, you can't play both sides of this game. You've got to decide if you're with us or with them,"' Romney said during a campaign stop. "'If you're with them, that will have a very significant consequence. If you're with us, that's very good thing."'
Romney did not clarify what that consequence might be.
The comments are among his toughest regarding Pakistan and represent a departure from his position last time he ran for president.
In 2007, Romney was critical of then-Democratic candidate Barack Obama's support for military action inside Pakistan's borders in some cases. Relying largely on drone attacks, Obama has pursued the policy as president, inside Pakistan and elsewhere.
Romney and other Republican presidential candidates last week praised the Obama administration's killing of a top al-Qaida operative inside Yemen.
Romney also took aim at Obama for suggesting in a recent television interview that American competition had gone "soft."
Obama's comments came last week on a Florida television station while talking about the need for investment in science and infrastructure and improving education.
"This is a great, great country that had gotten a little soft and didn't have that same competitive edge that we needed over the last couple of decades," Obama said during the interview. "We need to get back on track. I still wouldn't trade our position with any country on Earth."
Romney pounced Monday night.
"We have not gone soft. We have gone soft on the president too long," he said. "And it's time for us to get hard on him."