President Trump’s special envoy for North Korea negotiations said Monday that the United States would not agree to a phased approach for Pyongyang’s denuclearization.

“We are not going to do denuclearization incrementally,” Stephen Biegun said in his first public remarks since last month’s summit between Trump and North Korean leader Kim Jong Un. “The president has been clear on that, and that is a position around which the U.S. government has complete unity.”

{mosads}His comments, made at the Carnegie International Nuclear Policy Conference, appear to be a shift from a speech he made prior to Trump and Kim’s Hanoi, Vietnam, summit in which he said, “We are prepared to discuss many actions that could help build trust between our two countries.”

Still, Biegun on Monday denied a hardening of the U.S. approach to North Korea.

“The Trump administration position has not hardened,” he said.

Biegun’s remarks come as post-Hanoi headlines rack up about North Korea rebuilding the Sohae Satellite Launching Station in what analysts say is an apparent message to the United States.

Kim agreed to dismantle the site at the first summit with Trump in Singapore last year and began doing so after the meeting. But commercial satellite imagery taken after the Hanoi summit shows the site is back to operational status.

The latest images, taken Friday and released Saturday, show activities that could be consistent with preparations for a satellite rocket launch, according to an analysis by the Center for Strategic and International Studies’s Beyond Parallel program.

“Based on past practices, these activities could be consistent with preparations for the delivery of a rocket to the launch pad or engine to the test stand; or, they could be North Korean coercive bargaining tactics after the failed Hanoi summit,” the Washington-based think tank wrote.

In Monday’s remarks, Biegun said the United States does not know what Kim’s intention is regarding activity at Sohae.

“The short answer is, we don’t know,” he said. “We don’t know that it’s intended to send any particular statement to us.”

He also reiterated that Trump would be “very disappointed” if a launch were to occur.

Biegun stressed during the address that “diplomacy is still very much alive.” He did not offer specifics for when new talks might be held.