"Tourism, I can tell you this - tourism, you're going to go up like 10-fold with the expenditure of no money so I congratulate you", Mr Trump is heard saying on a speakerphone in a video posted to Facebook by Guam's Governor Eddie Baza Calvo.
"We are with you 1,000 percent", Mr. Trump said in the call to Mr. Calvo, who invited the president to the island.
After the tourism discussion, the two talked more about North Korea and how to deal with someone like Kim Jong Un and about partisan rancor and obstructionism in Washington, D.C.
Mr. Calvo, however, told Mr. Trump that he had "never felt more safe or so confident than with you at the helm".
Mr Trump agrees, saying "They should have had me in years ago. frankly you could have said that for the last three presidents".
Trump continued to exchange pleasantries with Calvo, saying that the governor had "become famous", and suggesting that he would visit the U.S. territory in the future.
"Guam is more than a military base. We reassure potential visitors that we continue to be a safe. place to visit".
"In this rhetorical back and forth, the North Koreans will do what you expect".
Despite Mr Trump's reassurances, Guam's security agency has issued a fact sheet with advice on what residents should do in the event of a nuclear attack. "We are not just a military installation".
I just got off the phone with Chief of Staff General John Kelly and with the President of the United States of America.
"I wish there would be less partisanship up there, this is a time of threats to the United States", said Calvo. "The wonderful island of Guam is very well protected".
Guam Gov. Eddie Calvo says officials haven't raised the US territory's threat level even after Pyongyang laid out plans to strike near the island.
In addition to the USA military bases, Guam is also equipped with the sophisticated Thaad weapons system which is capable of destroying intermediate-range missiles in the final phase of flight.
Meanwhile here on Guam, the threat level remains unchanged.