President Donald Trump said Tuesday he fired national security advisor John Bolton, saying on Twitter that Bolton had "disagreed strongly with many of his suggestions."

But minutes later, Bolton in his own tweet said he "offered to resign" Monday night — and that Trump told him, "Let's talk about it tomorrow."

"I offered to resign last night. He never asked for it, directly or indirectly," Bolton said in a later text to NBC News.

"I slept on it, and resigned this morning."

Either way, the departure of Bolton, a hawk on Iran and North Korea, shocked Washington. The news sent crude oil future prices lower.

NBC News, citing a White House spokesman, reported that deputy national security advisor Charles Kupperman has been appointed acting national security advisor.

Bolton, who was named national security advisor to succeed H.R. McMaster in March 2018, is a harsh critic of Iran, and has advocated military strikes against that oil-rich nation.

White House press secretary Stephanie Grisham told CNBC, when asked if Trump's once-secret invitation to the Afghan Taliban to meet at Camp David for peace talks was the breaking point of his relationship with Bolton, said: "No — it was many, many issues."