WASHINGTON (Reuters) - U.S. President Donald Trump said on Thursday he expects a medical examination he is to undergo on Friday will go well and that he would be surprised if it did not.

Answering questions from reporters after an event on prison reform at the White House, Trump said with a smile, “It better go well, otherwise the stock market will not be happy.”

“I think it’s going to go very well. I’ll be very surprised if it doesn’t,” he said.

The medical checkup at Walter Reed Medical Center in nearby Bethesda, Maryland, will be the first for Trump since he took office nearly a year ago.

Trump’s medical exam was announced early last month after he slurred part of a speech in which he declared the United States recognized Jerusalem as the capital of Israel.

Michael Wolff, author of “Fire and Fury: Inside the Trump White House,” has charged in promoting the book that Trump lacked the mental fitness to serve as president, drawing fire from Trump, his aides and supporters.

Trump’s physical exam is not expected to include a mental acuity test.

White House spokeswoman Sarah Sanders told reporters the exam will be conducted by presidential physician Ronny Jackson.

A statement about the results will be released on Friday. At the White House on Tuesday, Jackson will give details on Trump’s health and take questions.

(The story was refiled to correct the spelling of the doctor’s first name to “Ronny” instead of “Ronnie” in the penultimate paragraph)