The Senate ordered "realistic" tests of the Bush administration's proposed missile defense system yesterday but balked at Democratic proposals to delay deployment until the tests are conducted and to require an evaluation by an independent testing office.

The Senate also voted, 93 to 4, to increase permanently the authorized size of the Army by 20,000 troops, to 502,400. The administration has temporarily expanded Army troop levels to more than 495,000 but opposes a permanent increase. The House voted earlier to expand the Army by 30,000 and the Marines by 9,000 over three years.

The missile defense votes amounted to a go-ahead for initial deployment of the first nine ground-based missile interceptors in Alaska and California later this year and signaled likely congressional support for about $10 million for the program in next year's defense budget.

Democrats, arguing that the planned national shield may not be effective in shooting down incoming missiles, wanted to require tests of the system's operation under realistic conditions, with the results to be evaluated by the Pentagon's chief of testing, Thomas Christie, whom they regard as independent from political pressures.

A proposal by Sen. Jack Reed (D-R.I.) would have had Christie's office oversee the testing and its evaluation. Reed's proposal would have required testing without specifying whether it should be conducted before or after deployment.

Under an alternative proposed by Armed Services Committee Chairman John W. Warner (R-Va.) and approved by a largely party-line vote of 55 to 44, "operationally realistic" tests will have to be conducted by October 2005, but with the evaluation to be made by the Pentagon's Missile Defense Agency.

Republicans argue that the system is needed to shield the country in case of a ballistic missile attack by North Korea, Iran or terrorist groups and could serve as a deterrent to attacks. But Democrats cautioned that a flawed system would be dangerous and wasteful. "You don't deter something with a system that may not work," said Sen. Carl M. Levin (Mich.), ranking Democrat on the Armed Services Committee.

A report two months ago by the General Accounting Office, Congress's investigative agency, said the system was "largely unproven" and called for more realistic testing.

Earlier in the day, the Senate, voting 57 to 42, rejected a proposal by Sen. Barbara Boxer (D-Calif.) to require operational testing before the system is deployed.

Warner's testing provision was included in the $447 billion defense authorization bill for next year that the Senate hopes to complete early next week.

The testing proposal of Sen. Jack Reed (D-R.I.) did not contain specifics.The alternative plan of Sen. John W. Warner (R-Va.) was approved.