Donald Trump has engaged in a furious exchange of tweets and counter-tweets with a Republican senator, saying he "couldn't get elected dog catcher" while the congressman fired back that the president was "utterly untruthful".
"#AlertTheDaycareStaff," tweeted Bob Corker, an outspoken Republican critic of Mr Trump.
Same untruths from an utterly untruthful president. #AlertTheDaycareStaff
— Senator Bob Corker (@SenBobCorker) October 24, 2017
The latest clash came ahead of Mr Trump's planned lunch with Republican senators on Capitol Hill as Congress turns its focus to overhauling the nation's tax code.
Early today, Mr Corker said on NBC's Today programme that the Republican-led Congress should set the course on taxes after Mr Trump dismissed at least one idea on retirement plans.
Asked if Mr Trump should leave the issue to Congress, Mr Corker said: "I think that's the best way for us to have success."
That prompted an angry Twitter response from the president, who wrote: "Bob Corker, who helped President O give us the bad Iran Deal & couldn't get elected dog catcher in Tennessee, is now fighting Tax Cuts...."
Bob Corker, who helped President O give us the bad Iran Deal & couldn't get elected dog catcher in Tennessee, is now fighting Tax Cuts....
— Donald J. Trump (@realDonaldTrump) October 24, 2017
...Corker dropped out of the race in Tennesse when I refused to endorse him, and now is only negative on anything Trump. Look at his record!
— Donald J. Trump (@realDonaldTrump) October 24, 2017
Mr Corker took to his own Twitter account to respond: "Same untruths from an utterly untruthful president. #AlertTheDaycareStaff."
Mr Corker, the Senate Foreign Relations chairman, has previously dubbed the White House an "adult day care centre" and said Mr Trump could be setting the nation on a path to World War Three.
Mr Trump has called him "Liddle' Bob Corker".
Isn't it sad that lightweight Senator Bob Corker, who couldn't get re-elected in the Great State of Tennessee, will now fight Tax Cuts plus!
— Donald J. Trump (@realDonaldTrump) October 24, 2017
Sen. Corker is the incompetent head of the Foreign Relations Committee, & look how poorly the U.S. has done. He doesn't have a clue as.....
— Donald J. Trump (@realDonaldTrump) October 24, 2017
...the entire World WAS laughing and taking advantage of us. People like liddle' Bob Corker have set the U.S. way back. Now we move forward!
— Donald J. Trump (@realDonaldTrump) October 24, 2017
Republicans and the Trump administration are determined to get tax legislation into law this year, and all sides seem to think they can unite around that goal.
Before the lunch, senator John McCain implicitly criticised Mr Trump, though not by name, for getting a military draft deferment during Vietnam for bone spurs in his foot, and the president spent much of August lashing out at majority leader Mitch McConnell, blaming him for the Senate's failure to pass legislation to repeal and replace Obamacare.
The tax plan crafted by Mr Trump and Republican leaders calls for steep tax cuts for corporations and potentially for individuals.
It would double the standard deduction used by most Americans, shrink the number of tax brackets from seven to three or four, and repeal inheritance taxes on multimillion-dollar estates.
But crucial details of the plan have yet to be worked out, notably what income levels would fit with each tax bracket.
AP