The United States will maintain its policy of putting maximum pressure on North Korea to compel it to rid itself of nuclear weapons and ballistic missiles, even though President Donald Trump said last week he will refrain from using the term "maximum pressure," the White House said Monday.

Press secretary Sarah Huckabee Sanders also said that a June 12 summit between Trump and North Korean leader Kim Jong Un in Singapore will start at 9 a.m. local time, in what will be the first-ever U.S.-North Korea summit.

"As the president stated, we have sanctions on. They're very powerful, and we would not take those sanctions off unless North Korea denuclearized," Sanders said, in an apparent effort to allay concerns among Japan and other U.S. allies that Trump's remark may serve to weaken U.S. and U.N. sanctions on the North.

"Our policy hasn't changed," she told the press at a briefing. "Our focus will continue to be on denuclearization."

After a meeting Friday with Kim Yong Chol, a close aide to leader Kim, at the White House, Trump said he does not want to use the term "maximum pressure" anymore because Washington and Pyongyang are "getting along."

Asked about a personal letter delivered by Kim Yong Chol, a vice chairman of the Central Committee of the North's Workers' Party of Korea, to Trump from Kim Jong Un, Sanders declined to comment beyond quoting the president as saying it is "interesting."

"We feel like things are continuing to move forward, and good progress has been made, and we're continuing to prepare for the president's summit," she said.

It will be the first encounter between a sitting U.S. president and a North Korean leader. The two countries do not have diplomatic relations.

U.S. and North Korean officials have made "significant progress" during preparatory talks, Sanders said, without elaborating.