THE US’S NEWEST nuclear stealth bomber has made its debut after years of secret development and as part of the Pentagon’s answer to rising concerns over a future conflict with China.

The B-21 Raider is the first new US bomber aircraft in more than 30 years.

Almost every aspect of the programme is classified.

As evening fell over the Air Force’s Plant 42 in Palmdale, the public got its first glimpse of the Raider in a tightly controlled ceremony.

It started with a flyover of the three bombers still in service: the B-52 Stratofortress, the B-1 Lancer and the B-2 Spirit.

Then the hangar doors slowly opened and the B-21 was towed partially out of the building.

“This isn’t just another airplane,” US defence secretary Lloyd Austin said.

“It’s the embodiment of America’s determination to defend the republic that we all love.”

The B-21 is part of the Pentagon’s efforts to modernise all three legs of its nuclear triad, which includes silo-launched nuclear ballistic missiles and submarine-launched warheads, as it shifts from the counterterrorism campaigns of recent decades to meet China’s rapid military modernisation.

China is on track to have 1,500 nuclear weapons by 2035, and its gains in hypersonics, cyber warfare and space capabilities present “the most consequential and systemic challenge to U.S. national security and the free and open international system”, the Pentagon said this week in its annual China report.

”We needed a new bomber for the 21st Century that would allow us to take on much more complicated threats, like the threats that we fear we would one day face from China, Russia, ” said Deborah Lee James, the Air Force secretary when the Raider contract was announced in 2015.

While the Raider may resemble the B-2, once you get inside, the similarities stop, said Kathy Warden, chief executive of Northrop Grumman Corp, which is building the bomber.

“The way it operates internally is extremely advanced compared to the B-2, because the technology has evolved so much in terms of the computing capability that we can now embed in the software of the B-21,” Warden said.

Other changes include advanced materials used in coatings to make the bomber harder to detect, Austin said.