The group Bold Nebraska sent out an email Wednesday, urging its supporters to sign an online petition that would ask President Barack Obama to deny federal approval.
The group pointed to a recent tar-sands oil pipeline leak in Arkansas as evidence that regulators should reject the Keystone XL.
The proposed Canada-to-Texas pipeline is at the center of a political battle. A coalition of environmentalists, Native Americans and some landowners are fighting the project. Oil companies, some labor unions and the Canadian government are pushing for project approval.
Circulators say the petition will be sent to Obama, Nebraska Gov. Dave Heineman, U.S. Secretary of State John Kerry and Keystone XL developer TransCanada.