The reports that the president instructed the former White House lawyer to do so come as Mr Trump and House Democrats have clashed over the Russia investigation report compiled by special counsel Robert Mueller.
Democrats have sought witness testimony from individuals like Mr McGahn, and have demanded that the Justice Department hand over the full Mueller report alongside all of its underlying evidence.
The White House, meanwhile, has largely resisted those efforts, and Mr Trump has repeatedly insisted that the report exonerated him — which it specifically did not do.
The president’s ask of Mr McGahn to resist the subpoena will likely mean that Democrats will vote to hold him in contempt, which Judiciary Committee chairman Jerry Nadler pledged to do last week when confronted with the prospect the witness would snub him.
But being charged with contempt could be a smaller price to pay for Mr McGahn, who could risk his career in Republican politics if he does not heed Mr Trump’s demands. Plus, his Washington law firm could be impacted if Mr Trump begins to urge his allies to withhold their business.
The portions of the Mueller report that have been released indicate that Mr McGahn was a key witness for the special counsel’s office, and cited him more than any other witness in the portion discussing whether Mr Trump attempted to obstruct justice.
Mr McGahn, during interviews with Mr Mueller’s team, detailed several instances in which Mr Trump attempted to use his position to protect himself from the Russia inquiry. In at least one instance, Mr Trump attempted to get Mr Mueller fired.