A federal judge said Tuesday he is leaning against temporarily blocking enforcement of a new Arizona law penalizing businesses that employ illegal immigrants.

U.S. District Judge Neil Wake did not rule, but he told lawyers in the case that he is likely to turn down a request from business groups for a temporary restraining order to stop the law from taking effect Jan. 1. Opponents argue the law is unconstitutional and places an unfair burden on employers.

The judge said a major factor in his reasoning against the business groups is the challengers' failure to initially include county attorneys — the officials who would enforce the law — as defendants early in the case along with state officials. The failure meant the prosecutors now have to rush to defend their legal positions, Wake said.

The interests of law-abiding workers also must be considered, the judge said. Illegal workers compete for jobs with legal workers and depress wages, Wake said.

Illegal immigration has become a key issue in U.S. politics over the past year and has only gained more publicity as Democrats and Republicans alike seek to make clear their stand on how to deal with the country's roughly 11 million illegal immigrants.

Arizona's measure was one of a handful enacted by some state and communities in a bid to tackle what critics say Congress has failed to address. Some of the measures have been challenged in court by civil rights groups.

The Arizona law was passed last June by the Republican-majority Legislature and signed by Democratic Gov. Janet Napolitano .

Under the law, violators caught knowingly employing illegal immigrants would have their business licenses suspended for up to 10 days. A second offense would trigger permanent revocation.

Wake scheduled a Jan. 16 hearing on the business groups' request for a preliminary injunction to block enforcement of the law. He set the hearing after lawyers for some county attorneys told him in court that their offices likely would not have any enforcement cases ready for court before Feb. 1.