WASHINGTON — Sen. Chris Murphy, D-Conn., on Sunday called on an anonymous whistleblower from the intelligence community to come forward as congressional Democrats investigate whether President Donald Trump improperly pressured the president of Ukraine to investigate former Vice President Joe Biden's son for political purposes.

"I think if an American president is asking another foreign leader to interfere in an American election," Murphy said in an interview on "Meet the Press," then there has to be consequences for that."

"This whole timeline is hard to figure out. And there may be someone who can tell us more about all of it, and that whistleblower individual has to come before Congress."

The call comes after reports that a U.S. intelligence officer had filed a whistleblower complaint related to a promise made by Trump to a foreign leader on a phone call. Little is known about the content of the complaint. The Washington Post has reported that the phone discussion involved Ukraine.

The Justice Department's Office of Legal Counsel advised the DNI whether to disclose the complaint, said an official, who would not say if Attorney General William Barr was involved.

As congressional Democrats spar with the White House over the release of the complaint, much of their concern has centered whether there's a connection between an administration decision to temporarily freeze military aid to Ukraine and the push by Trump's lawyer, Rudy Giuliani, to promote an investigation into a Ukrainian energy company with ties to Biden's son, Hunter.

Murphy told "Meet the Press" that Ukrainian President Volodymyr Zelensky raised concerns about the aid during a meeting earlier this month, and that the Ukrainian president later spoke with the delegation about what Murphy referred to as "overtures from the Trump administration." He added that Zelensky "gave me a very strong answer. He said they had no intention to get involved in an American election."

Trump and his allies have denied any wrongdoing.

Also appearing on "Meet the Press," Treasury Secretary Steven Mnuchin said that while he wasn't on the call in question, "there was no connection" between the aid and questions about Biden.

And Trump dismissed the reports during Friday comments in the Oval Office where he called for more scrutiny into Biden.

“It's ridiculous. It's a partisan whistleblower. They shouldn't even have information," he said.

“It doesn’t matter what I discussed. But I will say this — somebody ought to look into Joe Biden's statement because it was disgraceful, where he talked about billions of dollars that he’s not giving to a certain country unless certain prosecutors are taken off the case."

The Biden campaign has denied any impropriety by the former vice president. In a memo released this weekend, the campaign pointed to fact-checkers and a report from a Ukrainian outlet that all say Biden had been fairly expressing the American government's position when he pressured a prosecutor to resign.

And the former vice president addressed the controversy in Iowa this weekend, accusing Trump of ginning up controversy because "he knows I'll beat him like a drum, and is using abuse of power and every element of the presidency to try to smear me."

As Democrats continue to call for an investigation, Sen. Pat Toomey, R-Pa., preached caution on "Meet the Press."

“It is not appropriate for any candidate for federal office, certainly including a sitting president, to ask for assistance from a foreign country. That’s not appropriate. But I don’t know that that’s what happened here," he said.

"There might be a reasonable explanation for this, and there might be a troublesome one. And we should understand why that happened," he added when asked about the delay of the foreign aid.