DENVER -- Gov. Bill Ritter said Thursday he may ask voters to approve a tax increase next year for one of Colorado's big needs, but he's not sure yet which one it would be.

Ritter said higher education, transportation and health care all need more funding but he hasn't determined which need is most pressing.

"I think it has to be about one thing, and we have to decide what that priority is," he told the Legislature's Joint Budget Committee, which sets state spending priorities.

"I don't think we can put the three things -- higher education, transportation, health care -- on the ballot," he said. "I think that's unfair to the voters; I think it would demonstrate a lack of leadership on my part and on the part of the Legislature."

Ritter said he has committees studying the issues and will wait for their recommendations before he decides.

This proposal comes just two years after voters approved Referendum C, allowing the state to keep its budget surplus for health care and education.

The governor also defended his executive order granting the 49,000 state government employees the right to join unions.

Ritter said the decision won't increase the budget and won't take away the power of lawmakers to set the budget.

Sen. Steve Johnson, a Fort Collins Republican and a budget committee member, told Ritter the state has done well by its employees, offering one of the most generous pay packages in the country.

Ritter's budget director, Todd Saliman, said Ritter held back on recommendations to increase the state's share of health, life and dental insurance for state workers so he could put more money in achievement pay that would cover all state employees.

Ritter went before the budget committee to discuss his estimated $18 billion spending plan, which would take effect July 1. He is proposing a $900 million increase in total state funding.

His plan recommends a $7.5 billion general fund appropriation, a 6 percent increase from this year's $7.1 billion and the maximum increase allowed by the state constitution.

Among the items in the budget is $59.5 million for higher education -- an 8 percent increase, money to add 14,000 children to the Children Basic Health Care Plus program and $500,000 to hire people to monitor county foster care programs.

The budget also includes money to replace 537 state fleet vehicles with hybrids and $2 million for rebate and incentive programs to encourage people to install solar panels.

"I do believe this budget is, in fact, conservative. It reflects the morals, values of the state with public safety, public education and health care being vital services we provide to public," Ritter said.

This is his first comprehensive budget since taking office in January.