COLUMBIA, Mo. -- A powerful Missouri state senator Tuesday unveiled a $2.8 billion plan to widen Interstate 70 to at least three lanes across the state, an even more ambitious proposal than what the governor originally asked of lawmakers.

Senate Appropriations Committee Chairman Lincoln Hough added the plan to a draft state budget for the upcoming fiscal year during a committee hearing.

Half the project would be funded with bonds. Hough estimated the state would pay around $132 million a year for at most 15 years to pay off the expansion.

Republican Gov. Mike Parson earlier this year asked lawmakers for $860 million to expand I-70 in the most congested areas: suburban St. Louis, Columbia and suburban Kansas City.

House lawmakers initially balked at the request but Tuesday gave initial approval to another budget bill that includes $860 million for the interstate. The House also Tuesday voted to spend $28 million on Interstate 44 improvements, along with a $20 million environmental impact study that's needed before more expansive work can be done on the roadway.

Proposals have existed for years to widen I-70 from two to three lanes in each direction across the entire state, but Missouri has never had the money to do it.

Lawmakers now have an opportunity to tap into the state's historic budget surplus to make that happen.

Hough urged fellow lawmakers to pump more money into I-70, citing current rates on government bonds and Missouri's few outstanding debts.

"The infrastructure improvements that we can make right now given the cash balances we have are transformative," Hough said.

An Associated Press request for comment to Parson's office was not immediately returned Tuesday.

The committee and the full Senate still need to vote on Hough's plan. If passed, the budget bill would head back to the House for another vote before it could go to Parson's desk for approval.

Lawmakers face a May 5 constitutional deadline to pass a budget.