Washington (CNN) The White House and State Department both stated Wednesday that the US is not ready to begin talks with North Korea, a day after Secretary of State Rex Tillerson had suggested the two sides could start negotiating without preconditions.

Tillerson's offer Tuesday to "sit down and see each other face to face" seemed to signal a shift in State Department policy, but US officials have since emphasized that North Korea has not yet demonstrated it is serious about talks or changing its behavior.

"We are open to the possibility of dialogue with North Korea, with the aim of denuclearizing the Korean peninsula. But North Korea must first refrain from any further provocations and take sincere and meaningful actions toward denuclearization," a National Security Council spokesperson told CNN.

"As the secretary of state has said, this must include -- but is not limited to -- no further nuclear or missile tests," the spokesperson said, adding, "Given North Korea's most recent missile test, clearly now is not the time."

Tillerson's specific reference to "no preconditions" has raised questions as to whether a rift exists within the Trump administration over possible negotiations with Pyongyang.

"We've said from the diplomatic side, we're ready to talk anytime North Korea would like to talk," Tillerson said at the Atlantic Council in Washington on Tuesday, in what seemed to amount to a direct public invitation for North Korea to put aside an escalating cycle of tests and taunts to engage in diplomacy.

"We are ready to have the first meeting without precondition," Tillerson said. "Let's just meet, and we can talk about the weather if you want. Talk about whether it's going to be a square table or a round table, if that's what you are excited about. But can we at least sit down and see each other face to face, and then we can begin to lay out a map, a road map of what we might be willing to work towards."

The remarks are some of the most concrete issued by Tillerson on what talks with North Korea might look like.

"I think Tillerson is saying, we are prepared to talk, we are not putting any conditions," said Ambassador Joseph DeTrani, former US special envoy to North Korea.

"But when we sit at the table, please don't launch missiles, don't have nuclear tests and maybe we can see what you want, you can put your requirements on the table and then you could listen to us," he added.

Some former US officials have raised doubts over whether Tillerson and the White House are on the same page.

"It is somewhere between confusing and worrisome," according to Evan Medeiros, a former National Security Council senior director for Asia.

"The State Department and White House should be in lockstep when it comes to issues like negotiating with North Korea," he added. "So if the White House is not backing up Tillerson, it suggests that Tillerson himself is trying to push the White House in the direction of just getting talks started, and perhaps Tillerson doesn't fully appreciate all the downside risks associated with talks without any kind of presteps or preconditions."

Tillerson has routinely appeared at odds with President Donald Trump over potential talks with Pyongyang. Earlier this year, Trump tweeted that Tillerson was "wasting his time" negotiating with North Korea.

When asked about Tillerson's Tuesday comments, the White House said, "The President's views on North Korea have not changed."

"North Korea is acting in an unsafe way not only toward Japan, China and South Korea, but the entire world. North Korea's actions are not good for anyone and certainly not good for North Korea," Sarah Sanders, the White House press secretary, said in an email Tuesday evening.

Both the White House and State Department said Wednesday that the administration remains united in its policy on North Korea and that any negotiations must wait until the regime shows it is willing to meet "international norms" that make talks possible.

"The policy has not changed -- I just want to be very clear on that," State Department spokeswoman Heather Nauert said Wednesday.

"We remain open to dialogue when North Korea is willing to conduct a credible dialogue on the peaceful denuclearization of the Korean peninsula," she added. "We are not seeing any evidence that they are ready to sit down and have those kinds of conversations right now."

"When somebody is shooting off ballistic missiles, when someone is conducting advanced nuclear tests, they're not showing any kind of interest or seriousness in wanting to talk," Nauert said. "At some point, we would like to do that, but our policy has not change."

But key questions remain, according to Kingston Reif, the director for disarmament and threat reduction policy at the Arms Control Association.

"Does Tillerson speak for the administration? And what would we be willing to put on the table in return for sustaining a testing freeze and more comprehensive talks?"

US National Security Adviser H.R. McMaster, one of Trump's most trusted foreign policy aides, said Tuesday that the global community must "make the most out of what might be our last best chance" to avoid military action, echoing comments he previously made that "time is running out."

Those comments may be more indicative of the administration's actual policy on North Korea, as Tillerson is believed to have been marginalized in the policy-making process. Reports surfaced last month that the Trump administration was considering replacing Tillerson with CIA Director Mike Pompeo, though the White House pushed back when asked about the rumors.

"You need both sides to be credible in the good cop-bad cop routine for it to work. There are too many doubts about the weight and credibility of Tillerson," said Vipin Narang, an associate professor of political science at the Massachusetts Institute of Technology who's a member of MIT's Security Studies Program. "McMaster has the ear of the President and is much more credible."