Infighting plagues Senate Judiciary Committee's Russia investigation

— -- The Senate Judiciary Committee has hit something of a partisan stalemate in its investigation of Russia meddling in the 2016 presidential election, a potentially ominous portent for how the probe’s outcome might be viewed.

The breakdown has clearly been coming for weeks as negotiations between staff to the chairman and ranking member broke down over concerns that the probe was focusing too much on areas each side deemed to be too partisan.

“They can go ahead and do whatever it is they want to do,” declared a clearly frustrated California Sen. Dianne Feinstein, the panel’s top Democrat.

“We have decided that each side is going to take a course. ... Our focus is obstruction of justice and whether there was cooperation/collusion between the Trump administration and Russia,” she added.

Feinstein has grown more frustrated in recent weeks with what she has called the “slow” pace of committee action as it relates, for instance, to former Trump campaign manager Paul Manafort, someone the panel has threatened to subpoena for weeks.

“I’m not sure what it is. Sen. Grassley and I have gotten along, but their staff seems to want to take this into a different venue and that’s Hillary Clinton, and it’s [former Attorney General] Loretta Lynch. We think it’s collusion and obstruction of justice,” Feinstein said.

Committee Chairman Chuck Grassley, R-Iowa, brushed off suggestions that his committee’s investigation had totally ruptured along partisan lines.

“I’m doing what I do,” Grassley said, adding in reference to Feinstein, “She wants to do what she wants to do. And we’re doing a lot of things together.”

The chairman noted that he wants to probe more deeply into a controversial, 7-year-old Obama-era agreement that led to Russia owning a 20 percent stake in the U.S.’s uranium supply through a Canadian mining firm called Uranium One, which had U.S. holdings. Then-Secretary Hillary Clinton’s State Department approved the sale, with explosive allegations swirling around whether or not the Clinton Foundation profited tangentially from the deal. The Clintons have denied any wrongdoing.

“That involves an area that she may not want to go into,” Grassley said.

Indeed, when asked about the so-called Uranium One deal today, Feinstein said she had only read “a couple of articles” on it and was not prepared to discuss the topic.

Grassley’s investigative staff recently made public 13 letters the chairman sent, without sign-off from Feinstein, to a wide range of individuals highlighting some of the majority's priorities as it seeks its own path forward.

The letters, sweeping in scope, requested information as well as private interviews with committee investigators.

“The committee is investigating improper political influence or bias in Justice Department (DOJ) or FBI activities during either the previous or the current administration [and] the removal of James Comey from his position as director of the FBI,” one letter, sent to the current General Counsel at DOJ, as well as an Obama Justice Department official, reads, adding that the panel also wants “the DOJ’s and FBI’s activities related to Hillary Clinton, the DOJ’s and FBI’s activities related to Donald J. Trump and his associates, and the DOJ’s and FBI’s activities related to Russian interference in the 2016 election.”

The chairman is seeking testimony from a former top member of special counsel Bob Mueller’s investigative team as well.

Peter Strzok, one of the FBI's top investigators, tapped by Mueller to help lead the probe of Russian meddling in last year's presidential election, stepped away from his post in mid-August for reasons that have not been made public.

On Comey’s firing, GOP investigators are focused on Lynch, as well as the law professor to whom Comey gave his contemporaneous memos detailing concerns he had following alleged interactions with President Donald Trump.

Comey circumvented Lynch in his investigation of Clinton’s use of private email, and that circumvention figured in the case Deputy Attorney General Rod Rosenstein made for firing Comey.

One senior committee Democratic member told ABC News, “That’s just an excuse for Grassley to ask a bunch of questions about Hillary’s emails. That’s all it is.”

Both Grassley and Feinstein said there would be times when they would work together. Both, for instance, must approve any subpoenas.

One area where both sides might cooperate is on questions surrounding the June 9, 2016, Trump Tower meeting between Russian officials and top Trump campaign officials, including Donald Trump, Jr., who was hoping for dirt on Clinton, his campaign rival.

Grassley investigators sent letters to every known participant in the meeting, including the Russians.

Staff are free to sit in on any interviews, the senators said.

But already there is some confusion over whether or not the majority is still investigating possible collusion between Trump officials and Russian President Vladimir Putin’s government.

When asked if the majority was still investigating collusion, Grassley muddied the waters, first saying “yes,” but then adding, “based on the proposition that now what we’re doing on the Uranium One makes it very bipartisan.”

“I am disappointed,” Feinstein told reporters. “I hope that, as some time goes by, we’ll be able to work things out.”

Meanwhile, the separate Russia investigation being conducted by the Senate Intelligence Committee is still operating on a bipartisan basis with few signs of infighting.

Feinstein, a member of that panel as well, chalked that up to the probe being conducted “almost entirely by staff, so it’s totally different.”

Meanwhile, the traditionally bipartisan House Intelligence Committee has been plagued by infighting over its Russia investigation.

Republicans maintain they have found no evidence of collusion after dozens of interviews and charge Democrats with leading a fishing expedition against Trump that could continue into the midterm elections.

Democrats have accused the majority of rushing to wrap up the investigation prematurely and scheduling interviews before the committee has received relevant records from the relevant agencies, entities and individuals.

Earlier this week, Chairman Devin Nunes, R-Calif., who had previously stepped back from leading the Russia investigation after ethics complaints accusing him of disclosing classified information, announced a new investigation of the Russian uranium deal, blindsiding Democrats as they were interviewing Trump lawyer Michael Cohen in the committee’s secure meeting room.

The rift has some members concerned that the committee’s Republicans and Democrats will release separate reports with their own findings and conclusions about Russian efforts to influence the election.

ABC News' Benjamin Siegel contributed to this report.