WASHINGTON (CNN) -- Former Massachusetts Gov. Mitt Romney is hitting New Hampshire and Iowa airwaves this weekend with a new ad advocating against an "amnesty" policy for illegal immigration.

The ad's release comes a day after a bipartisan deal was reached in the Senate that puts current illegal immigrants living in the United States on the path to citizenship -- a policy conservative critics claim amounts to amnesty. One of Romney's chief rivals for the GOP presidential nomination, Arizona Sen. John McCain, backs the measure.

Though the ad does not refer to the measure specifically, Romney says, "Legal immigration is great. But illegal immigration that we've got to end -- and amnesty is not the way to do it."

The 60-second ad is derived from an answer to a question on illegal immigration and border security that Romney fielded at a town hall in New Hampshire in early April. It will run in both Iowa and New Hampshire throughout next week.

In late February, Romney became the first presidential candidate to air a campaign ad and has aggressively done so since. In the first quarter of 2007, Romney spent $1.7 million on ad production and placement, the Washington Post reported.

A spokeswoman for the campaign would not reveal the size of the latest buy.