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.

The latest clash came ahead of Mr Trump's lunch with Republican senators on Capitol Hill as Congress turns its focus to overhauling the nation's tax code.

It came after 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...."

It came after 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...."

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".

The Tennessee Republican senator said later that world leaders are "very aware" that much of what Mr Trump says "is untrue", and the president is "debasing our nation".

Speaking to CNN outside a congressional hearing room, he said: "The president has great difficulty with the truth on many issues."

Mr Corker, who is retiring, said Mr Trump "is obviously not going to rise to the occasion as president", and his tenure will be remembered for "the debasing of our nation, the constant non-truth-telling, the name-calling... it's very sad for our nation".

The president responded that Mr Corker decided to retire after Mr Trump refused to endorse him "and now is only negative on anything Trump. Look at his record!"