 -- Days after creating confusion over the Trump administration's North Korea policy, Secretary of State Rex Tillerson walked back his comments that the U.S. was ready to meet Kim Jong Un's regime for talks "without precondition," telling the United Nations Security Council Friday that there must first be "a sustained cessation of North Korea's threatening behavior... before talks can begin."

"North Korea must earn its way back to the table," Tillerson said. "The pressure campaign must and will continue until denuclearization is achieved. We will in the meantime keep our channels of communication open."

Questions about just where the U.S. stands on talks highlight what have been sharp differences voiced by Tillerson and President Trump on North Korea --and come amid reports the White House wants him out. Tillerson's comments today also followed the White House and State Department vociferously denying any change in policy.

Tillerson was addressing a special Security Council meeting on the North Korean threat called by the chair country Japan after North Korea fired its third intercontinental ballistic missile on November 28 -- a missile capable of reaching the entire continental United States, it said.

The North Korean ambassador to the U.N. sat mere feet away while Tillerson spoke.

Asked afterward about his changed language on whether North Korea must meet preconditions before any talks, Tillerson didn't answer directly, instead telling reporters the U.S. is "not going to accept preconditions for these talks." He was referring to proposals by other countries, including one from China and Russia that U.S.-South Korean joint military exercises be halted in exchange for a halt to North Korea's ballistic missile and nuclear testing.

Tillerson rejected that idea again and instead appeared to signal that the U.S. was simply waiting for North Korea to show it is serious about engagement.

"Our communication channels remain open. North Korea knows they're open. They know where the door is. They know where to walk through that door when they want to talk," he added during the brief press conference.

At the same time, he did not address whether a commitment from North Korea to denuclearize remained a sticking point for the U.S.

All of these questions on what the administration's policy is began when Tillerson told a Washington audience Tuesday that demanding North Korea give up its nuclear and ballistic missile capabilities before engaging in talks was "not realistic... They have too much invested in it."

"The President is very realistic about that as well," he added.

That's at odds with previously-stated Trump administration policy that had demanded that North Korea agree to give up its nuclear and ballistic weapons before the U.S. would agree to talks.

As Tillerson himself told reporters on August 1, "A condition of those talks is there is no future where North Korea holds nuclear weapons or the ability to deliver those nuclear weapons to anyone in the region much less to the homeland." President Trump has been even more vocal, railing against negotiations with North Korea for months.

"Presidents and their administrations have been talking to North Korea for 25 years, agreements made and massive amounts of money paid," he tweeted on Oct. 7. "[It] hasn't worked, agreements violated before the ink was dry, makings fools of U.S. negotiators. Sorry, but only one thing will work!"

Trump even tweeted at Tillerson that he was "wasting his time trying to negotiate with Little Rocket Man," a derogatory nickname the president uses for the North Korean leader. "Save your energy Rex," he added.

It is unclear if Tillerson has been trying to signal a shift this week -- or perhaps misspoke or went too far on Tuesday.

After the Security Council session, he evaded reporters' questions about the discrepancies.

"There's no daylight at all between the president's policy and the pursuit of that policy," he said Friday, while not addressing the differences between Trump and himself.

The White House has also denied any change to policies, with spokesperson Sarah Huckabee Sanders saying in a statement Tuesday night, "The president's views on North Korea have not changed."

State Department spokesperson Heather Nauert said repeatedly Wednesday that the policy has not changed -- and even contradicted what Tillerson said Tuesday about denuclearization. When asked whether it was no longer a precondition, she said, "If they’re not willing to denuclearize? No. That remains our goal. Our overall goal is denuclearization."