There’s no guarantee that President Barack Obama’s health care law will launch smoothly and on time, congressional investigators say in the first in-depth independent look at its progress.

But in a report to be released today, the congressional Government Accountability Office also sees positive signs as the Oct. 1 deadline approaches for new health insurance markets called exchanges to open in each state — in many cases over the objections of Republican governors.

Additionally, the report discloses that the administration had spent nearly $400 million as of March to set up the infrastructure of a system involving major federal agencies, every state, hundreds of insurance companies, and millions of citizens, among them many individuals seeking coverage for the first time.

“Whether (the administration’s) contingency planning will assure the timely and smooth implementation of the exchanges by Oct. 2013 cannot yet be determined,” the report concluded.

The administration is taking the lead in setting up the markets in 34 states, the report said — an effort unforeseen when the law was passed. The computerized clearinghouse for the entire system — a federal “data hub” designed to deliver real-time eligibility rulings — has only undergone initial testing. And states have yet to complete many of their assignments.

“Much progress has been made in establishing the regulatory framework and guidance required for this undertaking, and (the administration) is currently taking steps to implement key activities of the (exchanges),” the report said. “Nevertheless, much remains to be accomplished within a relatively short period of time.”

GAO also issued a similar assessment for small-business health insurance markets scheduled to open concurrently.

The study shows “this law isn’t ready for prime time, and come October millions of Americans and small businesses are going to be the ones suffering the consequences,” Sen. Orrin Hatch, R-Utah, said. Hatch is the ranking Republican on the Senate committee that oversees health care financing.

Health and Human Services Secretary Kathleen Sebelius has steadfastly maintained the new insurance markets will open on schedule in all 50 states and Washington, D.C.

Middle-class people with no access to job-based coverage will be able to buy private insurance, in most cases with new tax credits to help pay premiums. Low-income people will be steered to public programs such as Medicaid in states that opt to accept an expansion offered under the law. Coverage starts Jan. 1.

An estimated 7 million individuals are expected to sign up through the exchanges next year, while Medicaid rolls will grow by 9 million. Those numbers are projected to steadily increase as Americans get more familiar with the law and its benefits. Exchanges are supposed to deliver the same basic service, connecting consumers with new coverage, whether they’re run by states or by the federal government.