"I would first head to the US Supreme Court if Democrats try to impeach me," Trump said.

President Donald Trump threatened Wednesday to fight a possible impeachment effort by Congressional Democrats in the US Supreme Court.

That could be difficult -- the US constitution, and the court itself, have made clear that it has no role in impeachment proceedings, which represent the legislature's power to check wrongdoing by the president.

But Trump's tweet suggested the White House is taking seriously a debate among Democrats on whether to launch the process that could remove the president on the basis of evidence of obstruction of justice in the Mueller report released last week.

"The Mueller Report, despite being written by Angry Democrats and Trump Haters, and with unlimited money behind it ($35,000,000), didn't lay a glove on me. I DID NOTHING WRONG," Trump wrote.

"If the partisan Dems ever tried to Impeach, I would first head to the US Supreme Court."

Released on Thursday, Special Counsel Robert Mueller's final report from his Russia meddling investigation listed a dozen separate actions by Trump that supported obstruction allegations.

But Mueller demurred on concluding if they amounted to a crime, leaving that decision to Congress, where the House of Representatives has the power to impeach a president -- formally charge him -- and the Senate to find him innocent or guilty.

The constitution is clear on the process: the very first article gives the House of Representatives "the sole power of impeachment" and the Senate "the sole power to try all impeachments."

In a 1993 case testing those principles, the Supreme Court itself ruled unanimously that it did not have a role.

"Giving the Supreme Court a role in the impeachment process itself was carefully considered but deliberately and emphatically discarded" by the authors of the constitution, said Harvard law professor Laurence Tribe.

Democrats on Wednesday were still debating whether undertaking a politically divisive impeachment effort would be a good idea less than 19 months before the next presidential election.