Explained | Trump says Golden Dome system would cost Canada $61 billion: Here's what it will offer

President Donald Trump said on Tuesday he had selected a design for the $175 billion Golden Dome missile defense shield and named a Space Force general to head the ambitious program aimed at blocking threats from China and Russia.

US President Donald Trump said in a Truth Social post on Tuesday that a proposed Golden Dome missile defence shield that he has previously said Canada wanted to be part of would cost Ottawa $61 billion.

He also mentioned that he would waive the charges for Canada if it became the 51st US state.

President Donald Trump said on Tuesday he had selected a design for the $175 billion Golden Dome missile defence shield and named a Space Force general to head the ambitious program aimed at blocking threats from China and Russia.

Trump announced at a White House press conference that US Space Force General Michael Guetlein would be the lead program manager for an effort widely viewed as the keystone to Trump's military planning.

Golden Dome will "protect our homeland," Trump said, adding that Canada had said it wanted to be part of it.

Canada is looking at potential investments in US President Donald Trump's proposed $175-billion Golden Dome missile defence shield, Prime Minister Mark Carney said on Wednesday.

Carney, who won an April election in part by promising to stand up to the threat posed by Trump, said he had discussed the concept of the Golden Dome a couple of times with the president.

"We have an ability, if we so choose, to complete the Golden Dome with investments in partnership. And it's something that we are looking at, and something that has been discussed at a high level," he told a press conference.

"Is it a good idea for Canada? Well, it's a good idea to have protection for Canadians and Canada."

Carney declined to say how much Canada might spend if it decided to take part in the Dome project.

How will the Golden Dome work?

The aim is for Golden Dome to leverage a network of hundreds of satellites circling the globe with sophisticated sensors and interceptors to knock out incoming enemy missiles after they lift off from countries like China, Iran, North Korea or Russia.

"I promised the American people that I would build a cutting-edge missile defence shield to protect our homeland from the threat of foreign missile attack," Trump said when he made the announcement on Tuesday.

In April, the Pentagon asked defence contractors how they would design and build a network to knock out intercontinental ballistic missiles during the "boost phase" just after lift-off - the slow and predictable climb of an enemy missile through the Earth's atmosphere. Existing defences target enemy missiles while they travel through space.

Once the missile has been detected, Golden Dome will either shoot it down before it enters space with an interceptor or a laser, or further along its path of travel in space with an existing missile defence system that uses land-based interceptors stationed in California and Alaska.

Beneath the space intercept layer, the system will have another defensive layer based in or around the US. This is something the Pentagon's Missile Defence Agency looked into during the first Trump administration.

Is Golden Dome like Israel's Iron Dome?

"We helped Israel with theirs, and were very successful, and now we have technology that's even further advanced from that," Trump said, referring to Israel's Iron Dome missile defence system.

The short-range Iron Dome air defence system was built to intercept the kinds of rockets fired by the Palestinian group Hamas in Gaza.

Developed by Israel's Rafael Advanced Defence Systems with U.S. backing, it became operational in 2011. Each truck-towed unit fires radar-guided missiles to blow up short-range threats like rockets, mortars and drones in mid-air.

The system determines whether a rocket is on course to hit a populated area; if not, the rocket is ignored and allowed to land harmlessly.

Iron Dome was originally billed as providing city-sized coverage against rockets with ranges of between 4 and 70 km (2.5 to 43 miles), but experts say this has since been expanded.

How is it similar to then-President Ronald Reagan's Star Wars initiative?

"We will truly be completing the job that President Reagan started 40 years ago, forever ending the missile threat to the American homeland," Trump said on Tuesday.

The idea of strapping rocket launchers, or lasers, to satellites so they can shoot down enemy intercontinental ballistic missiles is not new. It was part of the Star Wars initiative devised during the presidency of Ronald Reagan. But it represents a huge and expensive technological leap from current capabilities.

Reagan's "Strategic Defence Initiative," as it was called, was announced in 1983 as groundbreaking research into a national defence system that could make nuclear weapons obsolete.

The heart of the SDI program was a plan to develop a space-based missile defence program that could protect the US from a large-scale nuclear attack. The proposal involved many layers of technology that would enable the United States to identify and destroy automatically a large number of incoming ballistic missiles as they were launched, as they flew, and as they approached their targets. SDI failed because it was too expensive, too ambitious from a technology perspective, could not be easily tested and appeared to violate an existing anti-ballistic missile treaty.

Who will build the Golden Dome?

Trump ally Elon Musk's rocket and satellite company SpaceX has emerged as a frontrunner alongside software firm Palantir and drone maker Anduril to build key components of the system.

Many of the early systems are expected to come from existing production lines. Attendees at the White House press conference with Trump named L3Harris Technologies, Lockheed Martin and RTX Corp as potential contractors for the massive project.

L3 has invested $150 million in building out its new facility in Fort Wayne, Indiana, where it makes the Hypersonic and Ballistic Tracking Space Sensor Satellites that are part of a Pentagon effort to better detect and track hypersonic weapons with space-based sensors and could be adapted for Golden Dome.

But Golden Dome's funding remains uncertain. Republican lawmakers have proposed a $25-billion initial investment for it as part of a broader $150-billion defense package, but this funding is tied to a contentious reconciliation bill that faces significant hurdles in Congress.

China, Russia and North Korea react to the United States' Golden Dome project

China is "seriously concerned" about the US Golden Dome missile defence shield project and urged Washington to abandon its development, a foreign ministry spokesperson said on Wednesday.

Russian Foreign Ministry spokeswoman Maria Zakharova said on Tuesday that the Golden Dome project undermines the foundations of strategic stability as it involves the creation of a global missile defence system.

North Korea's foreign ministry also criticised the Golden Dome missile defense shield project as a "very dangerous threatening initiative", state media said on Tuesday.

(With Reuters inputs)