By Susan Heavey
WASHINGTON (Reuters) - A senior Republican senator called President Donald Trump "utterly untruthful" on Tuesday in an exchange of insults on Twitter hours before the president was to meet with lawmakers on Capitol Hill to build consensus for tax reform.
Trump has asked his fellow Republicans who control Congress to pass a package of tax cuts including a deep reduction in the corporate income tax by year's end, and his meeting with Republican senators on Tuesday afternoon was aimed at shoring up support in his own party.
But hours before the meeting, Trump engaged in a distracting tussle with one of those senators, Foreign Relations Committee Chairman Bob Corker. Alienating any members of his own party could be costly for his legislative initiatives in the Senate because Republicans control the chamber by just a slim 52-48 margin.
"Bob Corker, who ... couldn't get elected dog catcher in Tennessee, is now fighting Tax Cuts," Trump, set to attend Senate Republicans' weekly lunch, wrote on Twitter.
"Same untruths from an utterly untruthful president. #AlertTheDaycareStaff," Corker shot back to Trump in his own Twitter post. The senator previously referred to the White House derisively as an "adult daycare center."
Corker, who has said he will not seek re-election next year, has openly feuded with the president for weeks, escalated his comments in a CNN interview, saying the president is consistently untruthful, has debased the United States and undermined its relationships around the world.
Corker in August said Trump had "not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate in order to be successful."
Corker warned Trump in a round of other television interviews against interfering in congressional efforts to finalize legislation to cut taxes and called his visit with Senate Republicans "a photo op."
"Hopefully, the White House will step aside and let that occur in a normal process," the Tennessee Republican and fiscal hawk told NBC's "Today" program. "That's the best way for us to have success."
His comments followed Trump's promise on Monday to protect a popular retirement program as Republican lawmakers seek ways to pay for their proposed $6 trillion in tax cuts.
The spat with Corker, as well as the president's previous squabbles with other Republican lawmakers, further complicates Republican efforts to hammer out a final version of the tax proposal, which was devised without the input of opposition Democrats.
Republicans comfortably control the U.S. House of Representatives, but can afford to lose only two votes within their own party in the Senate to win passage.
Trump has said he thinks he has the votes to pass the plan, although detailed legislation has yet to be unveiled.
Speaking on "CBS This Morning," Corker urged Trump and the White House to "let the tax-writing committees do their work ... and stay out of taking things off the table and really negotiating against the process before it even begins."
White House spokeswoman Sarah Sanders shot back.
"I think we need to let the president take the lead on this front," Sanders told Fox News. "This is a president who wants to be aggressive, wants to take big action. And if Senator Corker doesn't want to be part of that ... we're not going to let that get in the way of us moving forward."
Republican Senator Roger Wicker also defended Trump before the meeting, which he said could fill in the plan's details.
"I view it as a coming together," Wicker told CNN.
(Additional reporting by Makini Brice; Editing by Will Dunham)