Haley's first book, released in 2012 when she was governor of SC, was part of her launch as a national figure within the Republican party, and led to talk that year she might join the GOP ticket with Mitt Romney. "Look at the chemical weapons in Syria", Haley said.
"I think she's helped make it a much better position", the president said.
Her departure is the latest shake-up in the Trump administration ahead of the November midterm elections.
The meeting will be covered by a White House pool reporter. The White House is effectively announcing the exit of its most popular Cabinet-level official - the extremely rare one who has strong approval among both Republicans and Democrats - just before voters vote. She also moved quickly to squelch speculation about her political ambitions.
Trump told reporters that he is hopeful that Haley will return to the administration at some point, perhaps in a different capacity.
Another possible successor would be national security adviser John Bolton, who was unable to secure Senate confirmation after Bush nominated him. Haley in her availability with Trump said she won't run against Trump and will instead campaign for him. She informed her staff Tuesday, NPR's Michele Kelemen reports.
Describing her United Nations tenure as "fantastic" and "incredible", Trump was effusive in his praise for Haley. She cited US action on Syrian chemical weapons, trade deals, the arms embargo in South Sudan, U.N. sanctions against North Korea, pulling out of the Iran nuclear deal and moving the USA embassy in Israel to Jerusalem.
She has served at the United Nations since the start of Trump's presidency.
Haley, in turn, called her tenure at the United Nations "the honor of a lifetime", saying, "I have been such a lucky girl to lead the state that raised me, and serve the country I love so much". "I don't agree with the president on everything".
Born in 1972 in Bamberg, South Carolina, Nimrata "Nikki" Randhawa rose quickly in the southern state's politics, serving in its House of Representatives from 2005 to 2011 when she was elected governor.
Trump ventured outside of his core group of supporters when he announced his intent to nominate Haley, then-South Carolina governor, to the post of U.S. Ambassador to the U.N. Haley was an early and vocal critic of the President-elect during the long GOP primary, endorsing Sens. She was re-elected in 2014. She also gained a reputation as a racial conciliator after leading the campaign to take down the Confederate flag at the South Carolina State House in 2015.