Barack Obama’s pick to head the U.S. Department of Homeland Security promised a Senate panel Thursday to do more to deal with employers who knowingly hire undocumented workers.

But Janet Napolitano told members of the Senate Committee on Homeland Security and Government Affairs that she can’t promise them that more companies will be prosecuted. That decision, she said, is made by the Department of Justice.

During the hearing of more than two hours, Napolitano said she supports the goal of a federal law which requires states to come up with more secure driver licenses. She even signed an agreement as governor with the agency she hopes to head to have Arizona produce those licenses.

But Napolitano later signed legislation which bars Arizona from complying with the federal law because of cost. The governor said Monday she would use her position inside the administration to lobby for more resources for affected sates.

Napolitano also acknowledged under questioning from Sen. Susan Collins, RMe., the ranking Republican on the panel, that she has not completed two of the 10 provisions of Arizona’s own homeland security plan. But Napolitano said one of those  computerizing criminal records  is nearly done and the other to create a radio system that allows different “first responders’’ to communicate with each other faltered solely due to lack of cash.

And the governor said she believes border fencing makes sense especially in urban areas. She told senators, though, she would not recommend spending money to put up barriers along the entire U.S.Mexico border.

The only thing close to tough questioning related to contentions that Napolitano had no specific experience in counterterrorism. Napolitano said that is not true, pointing to her time as the U.S. Attorney in Arizona when her agency handled part of the investigation of the 1995 bombing of a federal building in Oklahoma City.

“As you may recall, the planning for that crime occurred within Arizona,’’ Napolitano said. “We were responsible for setting up the command center and all of the investigative measures that were taken in connection with that matter.’’

And Napolitano said she prosecuted a militia group that was filming federal buildings in the Phoenix area with the intent to simultaneously blow them up.

“Now, have I done that on a daily basis?’’ she said to committee Chairman Joe Lieberman, IConn.

“Fortunately, not,’’ she answered her own question. But Napolitano said she does have an understanding of the facets of the issue, including that not all intelligence initially received is accurate.

No committee member expressed opposition to Napolitano’s nomination. Lieberman said he is sending the her name directly to the Senate floor  without a committee vote  where it could be acted on as early as next week.

The issue of punishing employers was raised by Sen. Claire McCaskill, DMo., who charged the Bush administration “purposely looked the other way’’ when companies hired undocumented workers. She said charges are brought against only 10 percent of the firms where undocumented workers were found  and only 22 companies in the entire country were employers were fined over two years.

“You could find 22 is Missouri,’’ McCaskill said.

Napolitano said she shares her frustration.

“You have to deal with illegal immigration from the demand side as well as the supply side,’’ she said. “We do have employers who use the lack of enforcement as a way to exploit the illegal labor market to depress wages, to exploit workers in some cases, and that requires enforcement,’’ said Napolitano, whose department also oversees Customs and Border Protection, the agency which investigates cases of illegal hiring and conducting raids on offending businesses.

But the governor told McCaskill she’s in no position to actually force the issue of prosecution.

“We have to have appropriate agreements with the Department of Justice, the U.S. Attorneys offices, that they’re going to bring actual cases,’’ she said.. Napolitano promised, though, that if she’s confirmed to “begin a collaboration’’ with prosecutors “so that we can start moving actual prosecutable cases through the system.’’

She boasted of signing “the nation’s strongest employer sanctions bill’’ as governor, a measure that allows a judge to suspend business licenses of firms found guilty of hiring illegal immigrants; a second offense within five years puts it out of business. No charges have been filed against any company in the year the law has been on the books, however, at least in part because prosecutors claim they need additional powers.

Napolitano also said the agency she would control needs to do more about the threat of “cyberattacks,’’ where an enemy could cripple the nation’s computer networks.

“We are, in some important respects, at the beginning of attacking the attacks, as it were,’’ she said. Napolitano said the existing section of her agency which deals with that “is not heavily staffed.’’