The US has selected a design for the futuristic "Golden Dome" missile defence system, says US President Donald Trump, adding that it will be operational by the end of his time in office.

Just days after returning to the White House in January, Trump unveiled his intentions for the system, aimed at countering "next-generation" aerial threats to the US, including ballistic and cruise missiles.

An initial sum of $25bn (£18.7bn) has been earmarked in a new budget bill, although the government has estimated it will end up costing much more than that over dthe ecades.

Officials warn that existing systems have not kept pace with increasingly sophisticated weapons possessed by potential adversaries.

President Trump also announced that Space Force General Michael Guetlein will oversee the project. Gen Guetlein is currently the vice chief of space operations at Space Force.

Seven days into his second administration, Trump ordered the Defence Department to submit plans for a system that would deter and defend against aerial attacks, which the White House said remain "the most catastrophic threat" facing the US.

Speaking in the Oval Office on Tuesday, Trump said the system would consist of "next-generation" technologies across land, sea and space, including space-based sensors and interceptors. He added that Canada had asked to be a part of the system.

During a visit to Washington earlier this year, then-Canadian defence minister Bill Blair acknowledged that Canada was interested in participating in the dome project, arguing that it "makes sense" and was in the country's "national interest".

He added that "Canada has to know what's going on in the region" and be aware of incoming threats, including in the Arctic.

Trump added that the system would be "capable even of intercepting missiles launched from the other side of the world, or launched from space".

The system is partly inspired by Israel's Iron Dome, which the country has used to intercept rockets and missiles since 2011.

The Golden Dome, however, would be many times larger and designed to combat a wider range of threats, including hypersonic weapons able to move faster than the speed of sound and fractional orbital bombardment systems - also called Fobs - that could deliver warheads from space.

"All of them will be knocked out of the air," Trump said. "The success rate is very close to 100%."

US officials had previously said that the Golden Dome will have the aim of allowing the US to stop missiles at various stages of their deployment, including before they launch and while they are still in the air.

The many aspects of the system will fall under one centralised command, US defence officials have said.

Trump said on Tuesday that the programme would require an initial investment of $25bn, with a total cost of $175bn over time. The initial $25bn has been identified within his One Big Beautiful Bill on tax, which has not yet been passed.

The Congressional Budget Office, however, has estimated that the government could ultimately spend more, up to $542bn over 20 years, on the space-based parts of the system alone.

Pentagon officials have long-warned that existing systems have not kept pace with new missile technology designed by Russia and China.

"There really is no current system," Trump said in the Oval Office on Tuesday. "We have certain areas of missiles and certain missile defence, but there is no system... there has never been anything like this."

A briefing document recently released by the Defense Intelligence Agency noted that missile threats "will expand in scale and sophistication", with China and Russia actively designing systems "to exploit gaps" in US defences.