The primary super PAC supporting Ted Cruz's presidential bid is inching closer to going on television with attack ads targeting Donald Trump.

The super PAC, Keep the Promise I, was in the process of finalizing strategy and could begin airing television advertisements before the Feb. 1 Iowa caucuses to help Cruz respond to Trump's charge that the Texas senator is soft on illegal immigration. On Friday, the New York celebrity businessman unveiled a television ad that his campaign said would begin airing in Iowa, New Hampshire and South Carolina.

Cruz responded with a television spot that criticizes Trump for supporting "eminent domain," which allows the government to force individuals to sell their property to make way for infrastructure, such as a highway, or private developments, like a hotel. Keep the Promise I, which has bee focused on undercutting Sen. Marco Rubio of Florida, another Cruz rival, appears poised to join Cruz's nascent air war against Trump.

"We are ready to defend Cruz and expose Trump. Buckle up!" Keep The Promise I spokeswoman Kristina Hernandez told the Washington Examiner via email.

Late Friday, no reservations for television time had been made by Keep the Promise I, according to sources who track media buying, nor was there any anti-Trump independent expenditure filings made by the super PAC with the Federal Election Commission. Hernandez declined to elaborate on the group's plans.

Earlier this week, as the confrontation between Cruz and Trump escalated, Keep the Promise I circulated a digital ad that featured Trump saying nice things about Cruz. The spot showed visuals of Cruz and used audio of Trump introducing the Texan at a Republican event in 2014. The ad was pushed out via the group's sister super PACs: Keep the Promise, Keep the Promise II and Keep the Promise III. It hasn't migrated to television.

Trump led Cruz in Iowa in the RealClearPolitics.com average of recent polls, 29 percent to 26.4 percent. But many political insides give Cruz a slight edge over the billionaire real estate mogul and reality television star, citing a super ground game and grassroots support that is built around voters who are more likely to participate in a caucus election. Cruz and Trump spent the week trading barbs and endorsements.

Trump rolled out the backing of Tea Party heroine Sarah Palin; Cruz responded with conservative talk radio host Glenn Beck. Trump continues to question Cruz's constitutional eligibility for the presidency because he was born in Canada and suggest that he took improper loans to fund his 2012 Senate campaign. Cruz responded by calling Trump New York liberal who does not support conservative values or policies.

Trump's tough ad on immigration opened a new front in his scramble to outflank Cruz in Iowa. Cruz has built his campaign in part around his opposition to illegal immigration and the policy of "amnesty" for illegal immigrants. So has Trump, and his ad, which uses video clips of Cruz speaking in his own words, could be problematic for the senator if not rebutted effectively.

That's where Keep the Promise I, and Cruz's other super PACs could prove helpful. Federal prohibits super PACs from coordinating with campaigns, but can take cues by piggybacking on the message a candidate communicates on the stump and through approved ads.