Declaring that space is the new warfighting domain, President Donald Trump on Thursday vowed the US will develop an unrivaled missile defence system to protect against advanced hypersonic and cruise missile threats from competitors and adversaries.Trump said in a Pentagon speech that the US will do what it takes "to ensure that we can detect and destroy any missile launched against the United States anywhere, any time, any place".Trump did not mention Russia, China or North Korea in his roughly 20-minute speech. But the Pentagon's new strategy makes clear that its plan for a more aggressive space-based missile defense system is aimed at protecting against existing threats from North Korea and Iran and countering advanced weapon systems being developed by Russia and China.The new review is the first since 2010, and it concludes that to adequately protect America, the Pentagon must expand defence technologies in space and use those systems to more quickly detect, track and ultimately defeat incoming missiles.Acting Defence Secretary Pat Shanahan, who also spoke, said competitors such as Russia and China are aggressively pursuing new missiles that are harder to see, harder to track and harder to defeat.Specifically, the US is looking at putting a layer of sensors in space to more quickly detect enemy missiles when they are launched, according to a senior administration official, who briefed reporters on Wednesday. The US sees space as a critical area for advanced, next-generation capabilities to stay ahead of the threats, said the official, who spoke on condition of anonymity to disclose details of the review before it was released.The administration also plans to study the idea of basing interceptors in space, so the US can strike incoming enemy missiles during the first minutes of flight when the booster engines are still burning.Recognising the potential concerns surrounding any perceived weaponisation of space, the strategy pushes for studies. No testing is mandated, and no final decisions have been made.Congress, which ordered this review, already has directed the Pentagon to push harder on this "boost-phase" approach, but officials want to study the feasibility of the idea and explore ways it could be done.The new strategy is aimed at better defending the US against potential adversaries, such as Russia and China, who have been developing and fielding a much more expansive range of advanced offensive missiles that could threaten America and its allies. The threat is not only coming from traditional cruise and ballistic missiles, but also from hypersonic weapons.For example, Russian President Vladimir Putin unveiled new strategic weapons he claims can't be intercepted. One is a hypersonic glide vehicle, which could fly 20 times faster than the speed of sound and make sharp maneuvers to avoid being detected by missile defence systems."Developments in hypersonic propulsion will revolutionise warfare by providing the ability to strike targets more quickly, at greater distances, and with greater firepower," Lt. Gen. Robert Ashley, director of the Defence Intelligence Agency, told Congress last year. "China is also developing increasingly sophisticated ballistic missile warheads and hypersonic glide vehicles in an attempt to counter ballistic missile defence systems."Current US missile defense weapons are based on land and aboard ships. Trump and Vice President Mike Pence have both emphasized space-based capabilities as the next step of missile defence.Senior administration officials earlier signaled their interest in developing and deploying more effective means of detecting and tracking missiles with a constellation of satellites in space that can, for example, use advanced sensors to follow the full path of a hostile missile so that an anti-missile weapon can be directed into its flight path.Any expansion of the scope and cost of missile defences would compete with other defence priorities, including the billions of extra dollars the Trump administration has committed to spending on a new generation of nuclear weapons. An expansion also would have important implications for American diplomacy, given long-standing Russian hostility to even the most rudimentary US missile defences and China's worry that longer-range US missile defences in Asia could undermine Chinese national security.Asked about the implications for Trump's efforts to improve relations with Russia and strike better trade relations with China, the administration official said the US defence capabilities are purely defensive and the US has been very upfront with Moscow and Beijing about its missile defense posture.The release of the strategy was postponed last year for unexplained reasons, though it came as Trump was trying to persuade North Korea to give up its nuclear weapons.While the US continues to pursue peace with North Korea, Pyongyang has made threats of nuclear missile attacks against the US and its allies in the past and has worked to improve its ballistic missile technology. It is still considered a serious threat to America. Iran, meanwhile, has continued to develop more sophisticated ballistic missiles, increasing their numbers and their capabilities.