Image copyright Reuters Image caption Ronny Jackson gave Mr Trump a medical in January

US President Donald Trump has announced the resignation of Veterans Affairs Secretary David Shulkin and picked the presidential doctor to replace him.

Thanking Mr Shulkin in a tweet, he said he intended to nominate Rear Admiral Ronny Jackson, who gave him his first medical as president in January.

Unnamed officials told Reuters Mr Shulkin had become a distraction due to speculation about his future.

A Pentagon official, Robert Wilkie, will be the acting secretary.

It is the latest in a series of departures from Mr Trump's cabinet.

This month alone, he has replaced his Secretary of State, Rex Tillerson, and National Security Advisor, HR McMaster, while his top economic adviser, Gary Cohn, also left following discord over Mr Trump's plans to impose trade tariffs on steel and aluminium.

Why was Shulkin under a cloud?

Previously held in high regard in public by the president, Mr Shulkin's position had been under mounting pressure.

Image copyright Getty Images Image caption Mr Shulkin was the only Obama-era administration official within Mr Trump's cabinet

A report released in February from an internal watchdog found "serious derelictions by VA personnel" on a trip to Europe last year.

The report accused the secretary of improperly accepting tickets to the Wimbledon tennis tournament whilst on the visit and using the trip to sightsee.

He denied the accusations but agreed to comply with the report's recommendations, including reimbursing the government for his wife's airfare for the trip, which was more than $4,300 (£3,000).

Skip Twitter post by @realDonaldTrump I am pleased to announce that I intend to nominate highly respected Admiral Ronny L. Jackson, MD, as the new Secretary of Veterans Affairs.... — Donald J. Trump (@realDonaldTrump) March 28, 2018 Report

Skip Twitter post 2 by @realDonaldTrump ....In the interim, Hon. Robert Wilkie of DOD will serve as Acting Secretary. I am thankful for Dr. David Shulkin’s service to our country and to our GREAT VETERANS! — Donald J. Trump (@realDonaldTrump) March 28, 2018 Report

Verna Jones, executive director of the American Legion, told CBS Radio the organisation was sad to see Mr Shulkin go.

"We think that Secretary Shulkin had done a tremendous job for veterans," she said.

"Under Secretary Shulkin's leadership, the veterans agenda had been moved - and more than we could have expected."

How might the doctor fare?

Media playback is unsupported on your device Media caption President Trump has good 'genes', according to a White House doctor

Rear Admiral Jackson, 50, has worked as presidential physician to three presidents, serving George W Bush and Barack Obama before Mr Trump moved into the White House.

He comes to the veterans post, which entails running a vast department, with little administrative or political experience.

However, he has a wealth of military experience, having served with a Marine unit during the war in Iraq.

He caught public attention after Mr Trump's medical, telling reporters the president was in "excellent health".

Denny Geisman, a US army veteran, welcomed President Trump's choice of replacement.

"Maybe there can be some true good reform now, based on the fact that he's a rear admiral, he's a veteran and, you know, he's a doctor," he said. "If he's handling the president of the United States I would say he's qualified to handle and help other doctors handle us vets."