WASHINGTON (AFP) - Nasa announced it has pushed back the launch of the Orion, the spacecraft designed to replace the agency's aging space shuttle fleet, by one year to 2014. "The window of opportunity for us to accelerate Orion (for a 2013 flight) has closed," said Orion programme manager Jeff Hanley, speaking during the same conference call. Nasa had been hoping to launch Orion on its first mission in September 2013. Rick Gilbrech, Nasa associate administrator for the Exploration Systems Mission Directorate, told reporters during a telephone conference call that the delay was due to technical difficulties and a tight budget. "We are still confident the Constellation Programme will make its first flight to the International Space Station on or before 2014," said Gilbrech. "Since the programme's inception, Nasa has been working an aggressive plan to achieve flight capability before our March 2015 target," said Gilbrech, referring to a deadline set by Congress. The Orion is a component of the Constellation programme, a Nasa programme that includes new launch vehicles and a lunar lander. The new crafts will resupply the International Space Station and carry out other missions such as landing on the moon. But the current space shuttle fleet is scheduled to decommissioned in late September 2010, once the ISS is completed. Russian Soyuz spacecraft will be supplying astronauts aboard the ISS until the Orion crafts are in service. Nasa officials will in the coming months talk to suppliers and manufacturers in the Constellation program - including the Orion developer, aerospace giant Lockheed Martin - to modify the contracts and adjust to the new calendar, said Gilbrech.