The commitment would provide stability for a White House staff that has seen high turnover, unless either Trump or Kelly changes his mind.
Many of Trump's friends and advisers have concluded the president doesn't really want a chief of staff - and he has several confidants urging him to operate without one.
In the two weeks leading up to Trump's disruptive swing through Europe, senior aides predicted that Kelly had days or hours left.
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Kelly was appointed last July to succeed Reince Priebus, Trump's first chief of staff, after serving for the first six months of the administration as secretary of homeland security. Trump was reportedly having discussions with staff on who could replace Kelly.
Andy Card, chief of staff under George W. Bush, served for a little over five years.
The announcement coincided with the retired Marine Corps general's one year anniversary at the White House.
If Kelly stays on into 2019, he'll occupy the role during a re-election cycle, which is likely to downsize what already is a weakened role for him.
But relations between the two have improved in recent months amid signs that Kelly plans to stay on, aides said. Add Trump Administration as an interest to stay up to date on the latest Trump Administration news, video, and analysis from ABC News.