One reason for the early cost growth is that it is difficult to forecast the cost of development, and in general budget predictability improved when initial development milestones were achieved. By the mid-2010s, the U.S. contribution was still expected to cost US$8.8 billion. In 2007, the expected ESA contribution was about €350 million. With the U.S. and international funding combined, the overall cost not including extended operations is projected to be over US$10 billion when completed. On 27 March 2018, NASA officials announced that JWST's launch would be pushed back to May 2020 or later, and admitted that the project's costs might exceed the US$8.8 billion price tag. In the 27 March 2018 press release announcing the latest delay, NASA said that it will release a revised cost estimate after a new launch window is determined in cooperation with the European Space Agency (ESA). If this cost estimate exceeds the US$8 billion cap Congress put in place in 2011, as is considered unavoidable, NASA will have to have the mission re-authorized by the legislature.