More than a dozen U.S. senators are urging FIFA to block Russia from hosting the 2018 World Cup, citing the country's "aggression" in eastern Ukraine. 

Sens. Robert Menendez, D-N.J., and Ron Johnson, R-Wis., were joined by 11 senators in signing a letter to Josef Blatter, head of the Fédération Internationale de Football Association (FIFA) seeking a new host country. 

“With the goal of ending the crisis in Ukraine and ensuring a successful 2018 World Cup, we strongly encourage FIFA to deny the Putin regime the privilege of hosting the 2018 World Cup and make preparations for an alternate host country,” the senators wrote. 

It's been several years since Russia was chosen as the host country for the 2018 event -- Russia beat out England; a joint bid by Belgium and the Netherlands; and a joint bid by Spain and Portugal. 

But, citing "Russian aggression" over the past year in eastern Ukraine including "unmarked Russian troops and Russian-backed separatists," the U.S. senators said it is "unacceptable" for FIFA not to allow a vote on moving the 2018 competition. 

They noted that nearly half of the 2014 World Cup participants have joined international sanctions against Russia. 

Menendez is the top Democrat on the Senate Foreign Relations Committee. Johnson helms the Subcommittee on Europe.