Washington - Colorado's senators are pushing the Pentagon to start construction of a $1.6 billion plant to destroy mustard-gas weapons at the Pueblo Chemical Depot.

In a joint letter Wednesday, Sens. Wayne Allard and Ken Salazar noted that Congress last year provided $50 million to the depot and said the money could be used to start construction on such a facility.

"We understand a significant portion of these appropriated funds have not been spent and could be used to complete early construction activities," said the letter to Michael Wynne, acting undersecretary of defense.

But Pentagon leaders want to study other options, including transporting the waste to Utah. Colorado and Utah leaders are opposed to moving the 780,000 munitions.

For the next fiscal year, the Pentagon has asked Congress for about $32 million for the program, which also includes a site in Kentucky.