Nikki Haley's Resignation Adds to Record Number of Trump Administration Departures: Full List of Cabinet Exits

United States Ambassador to the United Nations Nikki Haley announced her resignation Tuesday, saying she will step down at the end of the year for reasons she did not specify.

"There's no personal reason. It's very important for government officials to understand when it's time to step aside," said Haley, who praised Trump for his foreign policy leadership. "I want to make sure this administration, this president, has the strongest person to fight."

Addressing speculation, Haley said she will not run as a primary challenger to Trump in 2020 and will instead be supporting the president, adding it was time for her to step down from her nearly decade-long service between being South Carolina governor and U.N. ambassador.

The ambassador's resignation came as a surprise with no forewarning, adding to the ever-growing list of Trump administration personnel turnovers the president has seen across top levels of his administration and the White House.

Haley's departure will mark the sixth Trump administration cabinet or cabinet-rank member to resign or be fired in the less than two years since Trump took office, already exceeding that of former President George W. Bush and on track to outpace former presidents Barack Obama and Bill Clinton. There are 24 members who comprise the president's cabinet and cabinet-rank positions.

Reince Priebus

White House chief of staff, January 20, 2017, to July 28, 2017. Resigned after speculation he would be fired by Trump, saying he believed the president "wanted to go a different direction." Current Chief of Staff John Kelly took Priebus's place.

Tom Price

Health and Human Services secretary, February 10, 2017, to September 29, 2017. Resigned after coming under investigation by the HHS inspector general for his use of private flights, costing the department hundreds of thousands of dollars.

Rex Tillerson

Secretary of state, February 1, 2017, to March 3, 2018. Fired for having a "different mindset, a different thinking" from the president, according to Trump. Tillerson reportedly learned the news after a top aide showed him the president's announcement on Twitter. Tillerson was replaced by the current secretary of state, Mike Pompeo.

David Shulkin

Secretary of Veterans Affairs, January 20, 2017, to March 28, 2018. Fired after a Veterans Affairs Inspector General report said he spent a greal deal of time sightseeing during a European work trip and inappropriately accepted Wimbledon tickets. A White House official told CNN that Shulkin's "distractions were getting in the way of carrying out the President's agenda." Trump planned to replace Shulkin with White House physician Ronny Jackson, but Jackson later withdrew his name from consideration amid allegations he behaved improperly while working for the White House medical unit.

Scott Pruitt

Environmental Protection Agency administrator, February 17, 2017, to July 5, 2018. Resigned under mounting pressure from more than one dozen ethics scandals related to alleged unauthorized spending on government trips.

Nikki Haley

U.S. ambassador to the United Nations, January 27, 2017, to December 31, 2018. Resigned for unknown reasons after saying it was time for her to step aside following a near-decade-long career as former South Carolina governor and U.N. ambassador.

The number of resignations and firings under Trump grows exponentially when counting other White House and administration positions outside of that 24-member group.

In a running tally kept by CNN, the list will now increase to include the 52 Trump administration staff members who have since been fired, resigned or left for unknown reasons. Those staff members include some high-profile advisers, department heads and national security advisers, such as former White House aide Omarosa Manigault Newman, former FBI Director James Comey, former White House Chief Strategist Steve Bannon, former National Security Adviser Michael Flynn and former White House press secretary Sean Spicer.

Following Pruitt's resignation in July, a study by the Brookings Institute showed that at the time, 57 percent of Trump's top 65 White House and administration positions changed.

While representing the U.S. as Trump's U.N. ambassador, Haley has at times taken a more hawkish tone on Russia than the president would have likely preferred, including calling for additional sanctions on Russia after its involvement in Syria's use of chemical weapons on Syrian citizens. Following the president's one-on-one meeting with Russian President Vladimir Putin at their Helsinki summit this summer, Haley said the U.S. would "never" trust Russia or Putin, a contrast from Trump's refusal to condemn the foreign adversary for prior election interference.

Should Haley want to return to work for the administration, Trump said she would have her pick of administration jobs.

"We're all happy for you in one way, but we hate to lose–hopefully you'll be coming back at some point but in a different capacity," Trump said. "You can have your pick."