Five hundred delegates - mayors, manufacturers, planners, builders and critics - last night plunged into a fourday effort to chart the economic future of America.

In the keynote address to the White House Conference on balanced National Growth and Economic Development, Secretary of Commerce Juanita M. Kreps said "a national development strategy, if we are to have one . . . must not become the captive of any single interest."

The conference, which will run through Thursday at the Sheraton Park Hotel, was authorized by Congress in 1976 in an effort to provide a common meeting ground for the conflicting views of cities and suburbs, the fast-growing Sun Belt and the declining Snow Belt, job-hungry union officials and worried evironmentalists.

The delegates - three-fourths of them picked by the governors of their states and the rest by conference officials - seem to provide that mix. But whether they can find enough agreement in the three days of small worshops and general sessions that will precede their meeting with President Carter on Thursday morning remains to be seen.

Kreps, whose department took the lead in organizing the conference, said last night that "cooperation and compromise" will be needed to achieve the "difficult trade-offs" required by a national growth policy.

She was seconded on that point by West Virginia Gov. John D. Rockfeller IV, chairman of the conference advisory committee, who said the "diversity" of American economic interests "sometimes has been used as an excuse" for unnecessary rivalry.

But both Kreps and Rockfeller emphasized their belief that the states must play a leading role in planning future economic growth - and not leave that task to Washington.

Rockfeller said "we have placed too much reliance on the federal government doing things we ought to be doing ourselves." Kreps added that "any proposed new directions for growth policy that failed to draw our the resources and authorities of our balanced state governments will surely fail."

Despite the improving economy, the secretary said, there are serious inequities and imbalances visible: "Unemployment, for instance, is twice as high for blacks as for whites. Shortages of computer programmers persist while English teachers are in surplus. Unemployment rates of 11 percent plague El Pasa, while Houston . . . has labor shortages. Sprawl, speculation and rapid growth have defaced some areas; decay, despair and lagging growth have blighted others."

Kreps' department has a major stake in the outcome of the conference, which is to submit formal recommendations to Carter later this year. Commerce is favored by administration officials as the centerpiece of a reorganized federal economic development effort, and the Economic Development Administration, within Commerce, won a big boost in funds in Carter's first budget.

But Kreps conceded in her speech last night that there is wide disagreement about the role of the federal government in promoting balanced economic growth.

"Ought government be admonished to keep its hands off?" she asked. "Should government limit its sole to that of supplier of information and advice? Should it create penalties and incentives through the federal tax system?Ought it to write regulations to protect our health, safety and natural environment? Or be a financial subsidizer and supporter of those who have been left behind?

"Or," she asked, "should government flex its muscles to the fullest and take on the role of comprehensive planner of national and regional growth?"

Those questions will be addressed in small workshops and in a series of debates beginning today and featuring Henry Ford II; Rep. Morris K. Udall (D-Ariz.); Reginald H. Jones, chairman of General Electric; and Vernon Jordan Jr., president of the National Urban League.

Luncheon and dinner sessions for the delegates will be addressed by the secretaries of agriculture, labor, and housing and urban development. President Carter will speak at the closing session Thursday morning.

On Wednesday, a pair of public forums will be held to hear spokesmen for groups that do not have conference delegates. All general sessions of the conference are open to the public.