ST. PAUL — Gov. Mark Dayton revealed Thursday he will seek legislative permission to hire an outside law firm to examine the financing behind the proposed PolyMet Mining Corp. copper-nickel venture in northern Minnesota before his administration would issue a final permit.

In an interview Thursday with The Associated Press, the Democratic governor said his administration would approach a joint House-Senate panel as soon as next month for sign-off. Dayton said he hopes to bring a firm aboard by January to conduct a financial review alongside the environmental permitting process already underway.

“I’ve made it clear to the company that their financial capability to build this and then to operate it was going to be a critical component of my decision of whether the project will go forward or not,” Dayton said.

Dayton said he wants proof PolyMet and its investors have the wherewithal to build and operate a copper-nickel mining operation that could cost $500 million or more. It would go beyond the financial assurance guarantees that officials plan to require the company to provide to cover cleanup costs down the road.