A Downing Street spokesperson said.
The Prime Minister spoke to President Obama on Thursday evening following agreement in Lausanne between the E3+3 and Iran. Both leaders agreed that the political framework agreed was a major accomplishment and praised the work of foreign ministers and officials in Lausanne.
They agreed that there would be hurdles over the coming two months as the finer detail was negotiated and that both their teams would continue to work closely together.
Both leaders reiterated their commitment to securing a lasting deal but only if it was the right deal.