A conservative group launched two weeks of television ads praising the pro-business record of Republican Senate hopeful Richard Burr (search) in a race considered wide open.

The $600,000 ad campaign launched Thursday by a Virginia group, Americans for Job Security (search), signals a high-stakes media barrage that national groups are expected to launch on behalf of both parties.

Burr is seeking the seat being vacated by Democrat John Edwards. The expected Democratic nominee, Erskine Bowles (search), was a White House chief of staff for former President Clinton.

With Republicans holding a slim majority in the Senate, and with a number of Democrats vacating Senate seats, the race between Burr and Edwards is considered up for grabs.

The ads prompted Bowles to call for both sides to disavow third-party spending on the race. Bowles said donors to Americans for Job Security are largely unknown and that spending by such groups weakens campaign finance reform.

"By taking advantage of loopholes in campaign finance laws, they have raised millions of dollars from unnamed sources and used that money to influence elections from Washington, D.C.," Bowles said Thursday in a letter to Burr.

Last week, days after Bowles' first campaign ads hit TV screens around the state, Burr questioned why Bowles was going on the air so early and at a time when he leads in the polls.

A Burr spokesman said Thursday that no decisions have been made on when Burr will release his own TV ads.

Burr had nothing to do with the Americans for Job Security ads, which are running on stations on Charlotte and Raleigh, spokesman Doug Heye said.

"Honestly, we don't know," he said. "These kinds of ads are ... by law independent so we have no idea where they come from or who does them."

The 30-second spots don't mention Burr's Senate bid but list the phone number for one of his congressional offices and encourage voters to call Burr and thank him for his pro-business votes.

"Our goal with this is to invigorate debate on appropriate issues. This issue is on trade," said Michael Dubke, president of Americans for Job Security.

Additional GOP-slanted ads may focus on health care and other topics, he said.

Dubke's group started in 1997 and has been closely linked with the insurance and health care industries.