Heather Wilson, secretary of the US Air Force, said on Friday that the US is closer to developing a hypersonic missile that travels at five times the speed of sound.

Wilson, speaking on Friday at the Centre for Strategic and International Studies, a Washington think tank, said an effort was being made to keep pace with other nations in the development of new missile systems.

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The US Air Force currently operates 80 satellites in space, the secretary added. Her comments followed reports suggesting Russia was also developing new missile systems after Washington announced plans to exit from the landmark INF Treaty.

Moscow and Washington had been accusing each other of violating the treaty long before the United States announced it was withdrawing from the pact, thereby giving Russia six months to choose between leaving the INF Treaty or following its rules. Russia has denied committing any violations and announced that it has started to develop new weapons systems in order to keep up with the US and China.

Russian officials cited by the Independent have said that this work should be completed by the end of next year and expect the new systems to be ready by 2021.

Washington might, however, still reconsider its withdrawal from the INF treaty “should Russia return to full and verifiable compliance,” the US disarmament ambassador Robert Wood told a UN-sponsored Conference on Disarmament in Geneva on Tuesday, adding that its “Russia’s final opportunity to return to compliance.”