U.S. railroad customer groups have demanded regulators block or put onerous conditions on the proposed merger of Union Pacific and Norfolk Southern , the Financial Times reported on Sunday.

The Union Pacific and Norfolk Southern corporations announced Tuesday the companies will merge to create America's first transcontinental freight railroad.

When Union Pacific and Norfolk Southern announced their merger deal Tuesday to form “America’s first transcontinental railroad,” it puzzled some who recalled the golden spike driven in 1869 at Utah’s Promontory Summit. That last spike only connected two railroads from Omaha, Neb., to Sacramento, Calif.