weeks@ (Adds Mnuchin and Heitkamp quotes, background)
MANDAN, N.D., Sept 6 (Reuters) - U.S. President Donald Trump said on Wednesday he would get into "great detail" in the next two weeks on his U.S. tax reform plan, which has been short on specifics, even after months of discussions among administration and congressional leaders.
Trump, at a speech in North Dakota, listed his broad principles for tax reform as simplifying the U.S. tax code and providing tax relief to middle-class Americans, ideas he has been talking about since his 2016 presidential campaign.
"We're going to get into great detail over the next two weeks, but we're working on it with Congress now and coming up with very exacting numbers," Trump said.
The U.S. stock market rallied earlier this year on hopes of swift tax cuts for businesses under Trump, but analysts have since reduced expectations for major tax changes this year.
The Republican party is still divided on significant issues, such as whether or not tax cuts should be offset with spending cuts to avoid expanding the federal budget deficit and how deeply to cut the corporate income tax rate.
U.S. Treasury Secretary Steven Mnuchin, who accompanied Trump on the trip, said he expected the administration's tax plan to be considered by congressional committees later this month.
"We have a plan. The plan's being socialized with members," Mnuchin told reporters on Air Force One on the return to Washington. "Our expectation is it will be in the (congressional) committees later this month," he said.
Mnuchin is one of a six-member Republican team that has been negotiating a tax plan behind closed doors for months, excluding Democrats and producing only a few pages of basic principles. Some members of the team have recently tangled with Trump.
Trump economic adviser Gary Cohn is also a member of the "Big Six" team. According to sources close to the White House and an administration official, Trump has soured on nominating Cohn to lead the Federal Reserve.
That comes, two sources said, since Cohn criticized the president's response to the violence sparked by a white supremacist rally in Charlottesville, Virginia, last month.
McConnell, leader of the Republicans in the U.S. Senate, is also a Big Six team member. McConnell was attacked repeatedly last month by Trump on Twitter over Congress's failure to repeal and replace Obamacare.
Democratic Senator Heidi Heitkamp of North Dakota flew with Trump to her home state for the speech and was called on stage by the president along with Republican officials.
"Everybody's saying, 'Whats she doing up here?"' Trump said. "But Ill tell you what: Good woman, and I think we'll have your support."
Trump is trying to persuade Democrats to support his push to cut tax rates and simplify the tax code this year, a plan critical to bolstering Republicans heading into 2018 midterm elections, but which so far has included few details.
Heitkamp said in a statement that having Trump visit North Dakota was a good opportunity for the state to explain its priorities.
She said she was "open to working with Republicans and Democrats on comprehensive, permanent tax reform," but she cautioned that "the devil is in the details."
The White House plans to put Trump out on the road on a near-weekly basis this fall to sell his plan, which faces huge obstacles in Congress. Republicans control Congress but have so far been unable to pass Trump's top legislative priorities. (Reporting by Roberta Rampton; Editing by Lisa Shumaker and Kevin Drawbaugh)