Democrats and labor unions see the Bush administration changes as union-busting and political favoritism, and they pointed to problems at NASA as a red flag.

The procurement rules are among many revisions the administration is undertaking that do not require congressional approval. Officials are rewriting rules that determine which workers are entitled to overtime pay. They also are acting to allow religious groups that receive government money to discriminate in hiring based on religion.

Nearly half of the 1.8 million civilian government work force performs tasks that duplicate work in the private sector, the administration says. President Bush wants to let companies bid to provide that work, with at least 15 percent opened to competition by Oct. 31.

The regulations issued yesterday "will open much wider the doors to those businesses and their workers who can seek to provide to the American taxpayer a better value at a better price," said Mitch Daniels, outgoing director of the Office of Management and Budget.

Officials have identified examples of work being performed by government employees that they said probably could be done better and more cheaply by private businesses.

For example, 540 Navy workers make eyeglasses. In the Parks Service, rangers are being used to take money and tickets at the front gates.

Daniels could not say how many government jobs might be lost. He noted that agencies are allowed to compete with private companies for the work.

"We are indifferent as to who wins the competition," he said. "It need not result in any changes in federal employment. We'll just have to see what a more wide-open system brings."

The government's use of private contractors, however, is under examination at the National Aeronautics and Space Administration. A board investigating the explosion of the space shuttle Columbia is looking at whether NASA's heavy reliance on private contractors contributed to short cuts in maintenance inspections.

Bobby L. Harnage, president of the American Federation of Government Employees, said the rule changes "are merely an act to give lucrative government work to contractors without any accountability to the taxpayer."

Democrats, who are heavily supported by unions, have criticized the administration for lucrative contracts to reconstruct Iraq that have been awarded, with limited competition, to companies with ties to Vice President Dick Cheney and other prominent Republicans.

Current rules allow for public-private competition. But the regulations, which have not been significantly revised since 1983, are so cumbersome that private companies often are reluctant to seek government contracts, officials said.

The changes shortened the contract bidding process from as long as four years to one year, with many to be completed in just 30 days. Government studies show that savings of as much as a third can result from competition.

Sen. Edward M. Kennedy, D-Mass., an ally of organized labor, which stands to lose thousands of members if government jobs are lost, said such changes should be made by Congress.

"Reasonable steps to improve the efficiency of federal agencies make sense, but blanket privatization does not," he said. "We can't afford to hand over key federal responsibilities to companies with the best lobbyists or the lowest bids."

The Energy Department is among the agencies that has already opened jobs to private companies. Bidding is under way for such jobs as graphics design, computer technicians and financial services personnel.