WATCH: White House says U.S. will strike Iran 'harder' than ever if talks are unproductive

White House press secretary Karoline Leavitt insisted the U.S. is in ongoing talks even as Iranian officials deny it.

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"Talks continue. They are productive, as the president said on Monday, and they continue to be," Leavitt said at a White House briefing on Wednesday.

READ MORE: Iran dismisses U.S. ceasefire plan, issues counterproposal as strikes land across the Mideast

White House says more strikes to come if Iranian talks are unproductive

Saying that U.S. forces are "very close to meeting the core objectives" of the military action against Iran, Leavitt said that "productive conversations" with Iran were ongoing but stressed that more strikes could come if they're unsuccessful.

"If Iran fails to accept the reality of the current moment, if they fail to understand that they have been defeated militarily ... Trump will ensure they are hit harder than they have ever been hit before," Leavitt said at a briefing Wednesday.

Trump has said that U.S. was in talks with Iran to end the war as diplomatic efforts picked up, and Iran issued a newly defiant statement.

More from the White House on Iran talks

Leavitt declined to provide details on negotiations with Iran, saying it's a sensitive issue that remains in flux.

She said there are "elements of truth" in a 15-point plan said to have been put forward by the United States, but also said some reports have been "not entirely factual."

"I am not going to negotiate on behalf of the president here at the podium," Leavitt said. "What I will tell you is these talks are ongoing."

She cautioned White House reporters about "reporting about speculative points or speculative plans from anonymous sources."

"The White House never confirmed that full plan," Leavitt said, adding that "there are elements of truth to it, but some of the stories I read were not entirely factual."

White House maintains silence on who the US is negotiating with in Iran

But Leavitt declined to identify which Iranian or Iranians the administration is negotiating with. The press secretary also declined to comment on a 15-point ceasefire plan put forward by the United States that was rejected by Iran.

She cautioned White House reporters about "reporting about speculative points or speculative plans from anonymous sources."

"The White House never confirmed that full plan," Leavitt said, adding that "there are elements of truth to it, but some of the stories I read were not entirely factual."

White House says Trump plans to host Chinese president in Washington later this year

With Trump's trip to China now rescheduled for May 14 and 15, the White House is also talking about its intent to host the Chinese president in Washington later this year.

Trump had been scheduled to travel to China later this month but previously announced he was delaying the trip so he could be in Washington to help steward the U.S. and Israeli war against Iran.

When asked if the new dates for Trump's trip to China could suggest he believes the Iran war could end soon, his press secretary Leavitt offered an optimistic tone that the conflict could reach an endgame before he travels.

Leavitt also says the president and first lady Melania Trump plan to host Chinese President Xi Jinping and his wife for a White House visit later this year.