President Donald Trump plans to meet with the presidents of three Pacific island nations on May 21, a historic meeting that underscores the strategic importance of the Micronesian region.

They include Hilda Heine, president of the Republic of the Marshall Islands; Tommy Remengesau Jr., president of the Republic of Palau; and David Panuelo, who was elected May 11 as president of the Federated States of Micronesia.

All three nations have agreements with the U.S. called the Compact of Free Association that give the U.S. military control over their air space and surrounding waters.

“This will be the first time all three Freely Associated States (FAS) leaders are hosted together at the White House by a United States president, demonstrating the special partnership between the United States and the FAS,” the Department of the Interior said in a press release.

“The leaders plan to discuss the close security ties between the United States and the FAS, their shared commitment to democracy and the rule of law, and their mutual interest in maintaining a free and open Pacific.”

The Wall Street Journal reported that the meeting is part of an American effort to challenge increasing Chinese influence in the region.

It’s also part of an increasing military focus on the region, including nearby U.S. territories of Guam and the Commonwealth of the Northern Marianas.