Both Sens. Chris Coons and Tom Carper, D-Delaware, hailed the selection of former FBI Director Robert Mueller to lead an investigation into Russian election interference.

Both Coons and Carper said they were "encouraged" by Deputy Attorney General Rod Rosenstein's pick of Mueller to look into what role Russia played in the 2016 presidential election. 

"He has previous experience in stepping up to an overreach, an exercise of power by an administration and withstanding them," Coons told CNN's Anderson Cooper, during a satellite interview from WHYY's Wilmington studio Wednesday night.

Coons said Mueller's effort to stand up to Bush administration efforts to curtail civil liberties shows he can be an independent investigator. "He's also a decorated Marine veteran and someone who I think will enjoy the respect of a very wide range of members of Congress, so I think this is a positive and important step."

Carper has known Mueller personally for a number of years. "I believe he is guided by very strong core values," Carper said in a statement. "Throughout his career at both the FBI and the DOJ, he has committed himself to doing what is right, not what may be easy or expedient."

This investigation will not be easy or quick, according to Coons. "It could easily take months or well into several years, because the current FBI investigation has both a counter intelligence component and a possible criminal component," Coons said. "There's a lot of details to go through here, a lot of individuals to interview and a lot of documents to review."

While he's confident in Mueller's ability to get up to speed quickly, "the end results may be a year or two away," Coons said.