Virginia Gov. Bob Mc­Don­nell will propose a series of amendments to a bill that would require businesses to provide insurance coverage for children with autism, according to several legislators with knowledge of the changes.

The bill, passed by the General Assembly last month after 11 years of failed attempts, is strongly opposed by the business community, which considers the proposal a financial burden that companies cannot afford in tough economic times.

Mc­Don­nell (R) wants to make the bill more restrictive and less costly for businesses, legislators say. His staff has proposed as many as seven amendments and was speaking to the bill’s sponsors about them Monday.

The bill, as passed by the General Assembly, would require health insurers to pay for a specialized therapy known as applied behavioral analysis, as well as occupational, speech and other therapies, for children 2 to 6 years old. It would cap annual costs at $35,000 and apply to businesses that employ more than 50 people and are not self-insured. It would also cover public employees.

Virginia is set to join at least 23 other states that mandate insurance coverage for autism, having passed the bill with the support of House Speaker Bill Howell (R-Stafford).

But the Independent Insurance Agents of Virginia, the Virginia Chamber of Commerce, the National Federation of Independent Business and the Virginia Association of Health Plans oppose the bill.

Nicole Riley, acting NFIB state director, said her organization has been lobbying Mc­Don­nell to veto the bill. She said the group would appreciate amendments to lessen the bill’s impact on small businesses.

The Virginia Autism Project is sending e-mails and letters and making telephone calls to ask Mc­Don­nell to keep the bill intact.

Supporters say the legislation would cost businesses less than $1 per month per autistic child and would provide medical treatment when it can do the most good. The costs are estimated to range from $590,000 to $820,000 a year.

Mc­Don­nell has until midnight Tuesday to act. Legislators can accept or reject his amendments when they return to Richmond on April 6.