FRESNO, Calif. (AP) _ The Census Bureau has scaled back its dress rehearsal for the once-a-decade national head count, raising fears that thousands of soldiers, immigrants and other hard-to-reach people will go uncounted when the population survey is conducted in 2010.

"It's like sending up a rocket for a moon shot and not doing the final test on how to land," warned former Census Bureau Director Kenneth Prewitt, who oversaw the agency during the 2000 count.

The dry run is now under way in two states, with more than a half-million households receiving questionnaires from the Census Bureau. But the agency dropped such routine follow-up practices as sending census takers door-to-door to check whether homes on the bureau's mailing list are vacant or occupied, and dispatching workers to figure out the best way to reach soldiers on military bases.

Because the dry run helps shape the way the national head count is ultimately carried out, some politicians and demographers worry that the census will miss members of the military, inmates, homeless people, college students, migrant workers and immigrants, both legal and illegal.

Census Bureau spokesman Stephen Buckner said he is confident the 2010 count will be accurate. He said that bureau officials haven't eliminated any crucial portions of the simulation and that the census itself will feature the usual in-person interviews.

"We would have liked to have some more operational testing, but it didn't work out that way," he said.

The paring back was a consequence of a decision the Census Bureau made two weeks ago: Because of technology glitches and a bungled government contract, the bureau scrapped plans to send census takers out with handheld computers. Buckner said there wasn't enough time to train census takers to go out with pencil and paper in the test run, so the agency simply dropped the door-to-door part.

Since 1980, the bureau has organized a dress rehearsal to work the bugs out of its data collection methods. The one taking place this month in San Joaquin County, Calif., and nine counties surrounding Fayetteville, N.C., promises to be the sparest yet.

Unlike in past years, workers won't be sent out to double-check whether homes are occupied, and won't be knocking on doors to encourage residents to send in their completed questionnaires. Nor will the government test out the best time and manner to deliver thousands of forms to people living in group quarters, such as college dorms, prisons or military bases.

The government uses census data to determine how many representatives each state should get in Congress and to distribute hundreds of billions of dollars in federal aid.

"The cutbacks in the dress rehearsal will no doubt affect the accuracy of the 2010 Census," said Rep. Carolyn Maloney, D-N.Y. "The only question is how bad will it be and is there a chance to recover before 2010?"

The two areas hosting this year's rehearsal were selected because they contain a wide variety of people living in a multitude of circumstances. The Fayetteville area includes the Army's Fort Bragg. The Stockton, Calif., area some 60 miles east of San Francisco, residents speak dozens of languages at home. Stockton also has the highest foreclosure rate in the nation.

Prewitt who serves as a government adviser on the census said the data from practice runs is usually used to develop assumptions about housing vacancy rates and other conditions in the rest of the country. Without door-to-door visits, those extrapolations will be off, he said.

Also, without face-to-face contact, the bureau could have trouble understanding if its techniques are encouraging participation among immigrants, said William Frey, a demographer at the University of Michigan and the Brookings Institution.

"You've got an incredibly high amount of distrust of the government right now, and there are some significant obstacles that need to be overcome in this dress rehearsal," said state Assemblyman Felipe Fuentes, a Southern California Democrat. "An undercount in California would mean a severe reduction in our fair share of federal dollars."

In 1990, about 838,000 Californians went uncounted, and the state lost out on $223 million in Medicaid and other federal programs, according to the Government Accountability Office.

Buckner emphasized that the bureau has other reliable ways to verify vacancy rates, and said concern about uncounted immigrants is unfounded. The agency is working with community organizations and using the first-ever Spanish-English form, with one side in English, the other in Spanish, he said. (Census forms have long been available entirely in Spanish.)

Copyright 2008 The Associated Press.