Spicer also said that Trump will welcome NATO Secretary General Jens Stoltenberg to the White House on April 12 to "talk about how to strengthen the alliance to cope with challenges to national and international security."
The Belgian government had first announced last month that Trump would attend the meeting, which is separate from a NATO summit that takes place every two years for the heads of state and government.
During his campaign, Trump had called NATO "obsolete" and suggested that his administration might reevaluate U.S. support for the organization.
However, he has been more supportive since taking office. He declared his "strong support" for NATO during a news conference last week with German Chancellor Angela Merkel, but Trump went on to insist that member nations "owe vast sums" in dues and must pay more because the arrangement is "very unfair" to the United States. He appeared to be basing his criticism on an inaccurate understanding of how NATO funding works.
The administration raised eyebrows in Europe and in Washington on Monday after reports that Secretary of State Rex Tillerson was planning to skip the NATO foreign ministers' meeting this month to attend a planned meeting between Trump and Chinese President Xi Jinping at Mar-a-Lago, the president's winter estate in Florida.
The State Department and NATO said Tuesday that they were seeking an alternative date for a first meeting between Tillerson and alliance foreign ministers.
Tillerson is scheduled next month to make his first visit to Russia, where President Vladimir Putin has been eager to see the NATO alliance weakened.
Tillerson’s trip to Moscow, right after he flies to Italy for a meeting of ministers from the Group of Seven countries, comes at a time when the Kremlin’s alleged cyberattacks during the presidential campaign and meetings with several Trump campaign officials are being scrutinized by the FBI and Congress.