- What missile defense capabilities does Washington have? -

The United States relies on a network of satellites and early warning radar stations to detect and track missiles. They are currently deployed in the Aleutian Islands in the Pacific, Alaska, Britain, and Greenland.

There is also the Aegis Ashore air defense system based in the northern Polish town of Redzikowo that is capable of intercepting short- to intermediate-range ballistic missiles, as well as radar located in Deveselu, Romania.

Washington has several types of interceptor missiles, including the 44 GBI deployed in California and Alaska.

Those missiles are meant to "counter a threat from the Asian continent, but the GBI silos are not well positioned to intercept a threat coming from Russia," Etienne Marcuz, a researcher at the Foundation for Strategic Research, a French think tank, told AFP.

An intercontinental ballistic missile (ICBM) is launched by its engine to an altitude of several hundred kilometers. Once in space, it travels unpowered along a ballistic trajectory before releasing its warheads. The final phase of the flight involves the warheads re-entering the atmosphere.

If the goal is to protect against an Asian threat, it would make sense to deploy GBI missiles in the northeastern United States, not Greenland, Marcuz went on.

The researcher called Trump's idea of placing radar dishes and interceptors in Greenland merely "a pretext" to annex the Arctic island from NATO ally Denmark.

"There are already some in Poland and Romania, so that's not an argument."

The United States deploys SM-3 missiles on Aegis destroyers and at Aegis Ashore sites in Poland and Romania to intercept ballistic missile warheads after they separate from the booster, while the THAAD system is designed to target warheads in the upper atmosphere during their terminal descent.

- What is the Golden Dome project? -

Announced by Trump shortly after taking office, the Golden Dome project is intended to protect US territory against all types of missiles. The president plans to allocate $175 billion for the program, aiming to have an operational system by the end of his term -- a goal that many experts consider unrealistic within that timeframe.

Todd Harrison of the American Enterprise Institute estimates the project could cost around $1 trillion over 20 years, rising to as much as $3.6 trillion for a fully capable missile shield.

The centerpiece of the plan is a fleet of interceptor satellites in low Earth orbit, designed to leave orbit and collide with missiles during their flight through space.

"It's a multilayered system. In case of failure you need to have other firing options," said Marcuz, the French researcher. He added that Washington will also need to upgrade its missiles and interception capabilities on land and at sea.

- Why Greenland? -

Intercontinental ballistic missiles aimed at the United States would inevitably pass over the North Pole, he noted, so having detection radars and interception capabilities there would make sense.

The US military currently operates radar systems at its Pituffik base (formerly Thule).

Marcuz added that while "it's always useful to have radars in Greenland" in order to track missiles in space, "it will become less and less so."

"The United States is currently deploying SBIRS low-orbit satellites specifically to track missiles in their exo-atmospheric phase," he said.

Furthermore, the current defense agreements between the United States, Greenland, and Denmark already give Washington considerable leeway.

"The United States can position technical, material, and human resources in Greenland without limitation. They could even reposition nuclear assets if they wanted to," said Mikaa Blugeon-Mered, a researcher specializing in the geopolitics of the polar regions. "However, the key point is that the Danes and Greenlanders must be informed and consulted."

"If the Danes consulted on a project said 'no' and the United States proceeded unilaterally anyway, it could be interpreted as a violation of Danish sovereignty, and that would lead to a diplomatic and political escalation," he added.

"Therefore, Denmark doesn't have a veto right in the legal sense of the term, but in practice what the United States does in Greenland requires a political agreement."