U.S. Education Secretary Arne Duncan on Tuesday entered the preschool debate in Minnesota, urging lawmakers to invest in early-learning programs.

Duncan visited with preschoolers at Richardson Elementary School in North St. Paul. Joining him were Gov. Mark Dayton, whose top legislative priority is offering preschool to all four-year-olds in the state, Lt. Gov. Tina Smith, Minnesota Education Commissioner Brenda Cassellius.

The delegation spent about 10 minutes visiting with preschoolers before speaking with reporters.

Duncan entered the politically charged debate at a critical moment. Dayton, Senate DFLers and House Republicans are locked in a three-way battle over how — and how much — to fund early learning efforts, with few signs of compromise so far.

Dayton is pushing hard on a proposal that would make preschool a part of the public school system. The cost would start at $343 million for two years. His early-learning proposal also continues the $54 million in scholarships, which have funded 12,000 youngsters at private preschools, as well as at public schools offering pre-K programs.

The House GOP's recently-approved education bill ignored Dayton's universal preschool plan, preferring instead to support the existing network of private preschools. They would offer an additional $30 million in vouchers tied to a ratings system that helps parents assess the quality of preschool programs.

The Senate DFL is taking an altogether different approach, with a small $5 million boost for preschool vouchers, but $70 million for "school readiness" programs that offer individual schools maximum flexibility in determining how to prepare children for kindergarten.

Duncan expressed support for Dayton's universal preschool plan for four-year-olds. Duncan said it's important to also serve children from birth to age 3 to ensure they are prepared to enter kindergarten.

"I can't overstate how important this is, and I hope, I just really hope this state doesn't squander this opportunity," Duncan said.

"We have this false argument [over scholarships or universal preschool]," Duncan said. "If you could and you can provide this to every single child, my question is, 'Why wouldn't you do that?' "

Photo: U.S. Education Secretary Arne Duncan greets students at Richardson Elementary School in North St. Paul. (Ricardo Lopez/Star Tribune)