PHOENIX — The new leader of a federal immigration agency in Arizona said Thursday that a key element in his plans to confront the state's border woes is cracking down on employers who knowingly hire illegal immigrants.

Matthew Allen, the new chief of investigations for U.S. Immigration and Customs Enforcement in Arizona, said illegal immigrants would be less likely to come to the state if they knew employers wouldn't offer them jobs.

"We can't arrest our way out of this problem," Allen said. "No one in the U.S. government — whether that's (the Department of Homeland Security) or (Department of Justice) — has the capacity to arrest, go out and physically arrest, every alien who is here illegally."

That's why it's important to focus on the root cause of much of America's illegal immigration — jobs offered to immigrants, said Allen, who previously oversaw such efforts while serving at the agency's headquarters in Washington.

Allen investigated drug and immigrant smuggling groups as an agent in Nogales from 2000 to 2004. He said he also plans to take steps to combat drop houses.

Drop houses are where immigrant smugglers hide their customers and collect payments before sending them to spots across the country. Metropolitan Phoenix is believed to have about 1,000 drop houses.

Allen said he wants his staff to develop relationships in the real estate industry so they can provide advice on spotting drop house operators.

Other plans include balancing the daily needs of assisting state and local police agencies on immigration calls while continuing the federal agency's long-term investigations.

Allen replaces Alonzo Peña, who is moving to another post in the Department of Homeland Security.

Peña's 16-month tenure in Arizona was marked by his efforts to repair the agency's damaged relationships with state and local leaders.

Democratic Gov. Janet Napolitano, who had been critical of Peña's predecessor and the federal agency's staffing levels in Arizona, said the agency's operations in the state improved under Peña's leadership.

"We had real problems working with ICE under his predecessor," Napolitano said. "And (Peña) came in and was very good to work with overall, with the resources he was given. He can only do so much with what Washington, D.C., gives him, but I thought he did a very good, professional job. I enjoyed working with him."

Associated Press writer Paul Davenport contributed to this report.