The US president said the UK's decision to cede the Chagos Islands to Mauritius is among the reasons he wants to take control of Greenland.
Under the agreement, the UK will pay Mauritius €120 million each year to lease back their military base for at least 99 years.
Britain intends to hand over the Chagos Islands to Mauritius, while retaining a key UK-US military base on the island of Diego Garcia.
The UK will return the Chagos Islands to Mauritius, but Diego Garcia will remain under UK-US control. Chagossians, displaced decades ago, feel excluded from the deal.
After years of legal wrangling and negotiations, Britain said it would surrender sovereignty of the archipelago in the Indian Ocean.