How much longer will the Russia investigations take? Timetable divides lawmakers along party lines

— -- The ongoing investigations into Russian meddling in the 2016 presidential election led by both the special counsel and congressional investigators seem certain to stretch into 2018, but members of Congress are becoming increasingly divided over how much more time to spend on the probes.

While House Republicans have expressed a desire to wrap up their investigation before Christmas, ranking Democrat Rep. Adam Schiff of California told ABC News there are "dozens" of witnesses yet to be interviewed and “months of work” yet to be done.

“If we want to adhere to a political timetable the majority will bring this to an end, but it will be a tremendous disservice to the country,” Schiff said.

“There are dozens of witnesses who have clearly relevant testimony, so that's going to take time to do,” he said. “The worst thing I think we can do would be to make a report to the public that was incomplete and therefore misleading and have to explain why months from now what we told the public just wasn't true because we didn't want to find the evidence.”

There is a similar rift among members of the Senate Intelligence Committee, although less has been said about when their work would finish. The committee’s chairman, Republican Sen. Richard Burr of North Carolina, has said he expects to have the interviews wrapped by the end of the year and to have a report before the primaries, according to his staff.

Democrats have said privately they hope the work will continue until they have answers, even if that means taking more time.

Then there is the matter of the Special Counsel investigation. The Special Counsel’s office has given no indication of how long they expect their wide-ranging probe to last, though ABC News is aware of at least one witness who has been scheduled to meet with investigators in February.

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The trial for former Trump campaign manager Paul Manafort is currently scheduled for May 2018. And the regulations that govern the special counsel’s office require Mueller to provide a status report and budget to the Attorney General each fiscal year.

Right now, investigators are operating on a budget that has been approved through Sept. 30, 2018.

All of that comes long after the target date that White House officials have in mind for completion, with sources telling ABC News that President Trump expects a resolution by the end of the year or shortly after that.

Ty Cobb, one of Trump lawyers in the matter, told ABC News Wednesday that he appreciates the fast work of the Mueller team.

"The bulk of the credit frankly goes to the special counsel and his team and how seriously they take the fact of trying to expedite the interviews in an appropriate and thorough fashion regarding an inquiry of a president knowing the strain it puts on a country." Cobb said.