By Euan McKirdy

CNN

(CNN) -- US President Donald Trump will attend a NATO leaders' summit scheduled for May, the White House has confirmed.

"The President looks forward to meeting with his NATO counterparts to reaffirm our strong commitment to NATO, and to discuss issues critical to the alliance, especially allied responsibility-sharing and NATO's role in the fight against terrorism," a statement from the White House reads.

It added that, in addition to the Leaders Meeting, Trump will also host Secretary General Jens Stoltenberg at the White House next month, "where they will talk about how to strengthen the alliance to cope with challenges to national and international security," the statement adds.

The April meeting with Stoltenberg has been arranged to prepare for a May 25 summit in Brussels on the "new security environment, including the Alliance's role in the fight against terrorism, and the importance of increased defense spending and fairer burden-sharing."

The announcement of Trump's attendance comes on the heels of a decision by US Secretary of State Rex Tillerson to skip a NATO foreign ministers' meeting, and instead host Chinese President Xi Jinping later this month, before visiting Russia in April. The State Department has suggested "alternative dates" to NATO for the meeting.

Tillerson opt-out makes waves

Tillerson's decision not to attend the NATO meeting in Brussels next month has led to consternation amongst the US' European allies.

"Seeing the Chinese, then going to Russia and avoiding NATO in the middle -- it's weird," said one NATO diplomat. "It shows that they don't care about NATO. They are not multilateral."

"They probably didn't realize how much impact it would have if he didn't go," the diplomat said. "Now that everybody is screaming about him not going, maybe they will realize."

As one European ambassador to the US put it: "To say the least, everyone is in disbelief."

State Department acting spokesman Mark Toner told reporters Tuesday afternoon that the meeting's dates didn't fit in Tillerson's schedule and a NATO official confirmed that the group is still negotiating with the State Department to schedule the meeting. Toner said the agency is "certainly appreciative of the effort to accommodate Secretary Tillerson."

The official added that Tillerson's schedule isn't the only one they're coordinating on.

Tillerson to Congress: Ratify Montenegro

Meanwhile, Tillerson has been attempting to keep NATO commitments moving along ahead of May's meeting and keep American leadership relevant within the bloc.

On March 7, he wrote to Senate Majority Leader Mitch McConnell asking Congress to ratify Montenegro's membership in NATO.

While the invitation to invite Montenegro to join the alliance was unanimously approved by NATO allies, in the letter, obtained by CNN a day after news broke that Tillerson was skipping the April NATO meeting, the Secretary notes that the US is one of only four member nations which has not given parliamentary approval for the country's bid.

"Allies look to the United States for leadership within the Alliance," he wrote. "Montenegro's participation in the May NATO Summit as a full member, not an observer, will send a strong signal of transatlantic unity."

Rocky relations

While Trump last week reaffirmed the US' commitment to the bloc -- albeit with complaints about member countries' defense spending -- he has long been critical of the role NATO plays.

In a joint interview with the Times of London and German newspaper Bild, he called the organization "obsolete," and from a White House podium alongside German Chancellor Angela Merkel, said that "many (NATO allies) owe vast sums of money from past years and it is very unfair to the United States.

"These nations must pay what they owe."

The statement is a mischaracterization of the commitments that NATO members have -- under the treaty, countries in the bloc have agreed to target spending 2% of their GDP on defense, but do not accrue debts if they have not met these targets.

Tillerson, among other members of the Trump administration including Vice President Mike Pence, have been at pains to stress the official US line of cooperation with NATO and other global institutions.

However, Trump himself has repeatedly undermined the position, initially with declarations on the campaign trail and, since taking office, critical comments and tweets. Alongside his characterization of NATO as obsolete, he has been equally dismissive of the EU, another bulwark of western liberal democracy.

CNN's Nicole Gaouette, Michelle Kosinski and Elise Labott contributed to this report.