U.S. Sen. Amy Klobuchar pressed federal election officials Tuesday about the Justice Department's decision not to pursue possible campaign finance violations stemming from President Donald Trump's July 25 call with Ukraine's president, now the subject of a House impeachment inquiry.

Klobuchar, D-Minn., a candidate for president, wrote to Ellen Weintraub, chairwoman of the Federal Election Commission (FEC), seeking more information on how the agency has previously defined phrases like a "thing of value" and "anything of value," which federal prosecutors reportedly cited when declining to open a criminal investigation.

Democrats have accused Trump of soliciting banned foreign contributions during the July phone call when he asked Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden, one of his top 2020 challengers.

Trump's defenders have cast the exchange as a legitimate inquiry into foreign corruption and the business dealings of Biden's son, Hunter Biden, who was associated with a Ukrainian energy company while Biden was in the White House.

Klobuchar, the ranking Democrat on the Senate Rules Committee, which oversees the FEC, said the episode raises questions about the foreign contribution ban.

"What 'something of value' is, is key because … the standard of whether or not there is an election law violation is if you got something of value from it," Klobuchar said in an interview. "So by contacting foreign leaders to try to get dirt on opponents, you know, he's trying to get election information."

Klobuchar, in her letter, wrote that she wanted additional information "to clarify the fact that it is not only wrong — but also illegal — to solicit foreign assistance to diminish a political opponent."

Klobuchar cited special counsel Robert Mueller's report on Russian interference in the 2016 presidential election that found that "candidate-related opposition research" provided by foreign sources could violate federal laws governing elections.

The senator gave Weintraub an Oct. 18 deadline to respond to her request, which also seeks documents related to communications between the FEC and Justice Department. Klobuchar also requested an explanation as to why the Justice Department, in declining a criminal prosecution, did not refer the matter to the FEC for possible campaign finance violations.

Klobuchar also is seeking details on recent cases in which the FEC applied the Federal Election Campaign Act or "deadlocked on whether or not to apply the ban."

"When you have what I consider an election violation, you're supposed to go to the election commission," Klobuchar said in an interview. "And this would be in addition to the other concerns about security interests and breaking the law and putting a political campaign in front of the security interests of the country — which is I believe what happened here."

Stephen Montemayor • 612-673-1755 Twitter: @smontemayor