The Senate has voted to move forward with a bill setting aside more than 2 million acres in Michigan and eight other states as wilderness.

The 66-12 vote during a rare Sunday session marks an early partisan showdown that has threatened to derail pledges by Senate leaders to work cooperatively as a new administration takes office.

The bill is the largest expansion of wilderness protection in 25 years. It has bipartisan support and includes 11,739 acres in Pictured Rocks National Lakeshore along Lake Superior in Michigan's Upper Peninsula.

The Senate vote limits Republican stalling tactics and enables the bill to move forward. Senate approval is expected later this week.