Iranian President Hassan Rouhani warned U.S. President Donald Trump on Tuesday to stay in the nuclear deal Tehran signed with world powers in 2015, or face “severe consequences”, as other signatories stepped up efforts to save the agreement. Trump has said that unless European allies fix what he has called “terrible flaws” in the deal by May 12, he will restore U.S. economic sanctions on Iran, which would be a severe blow to the pact. The other powers that signed it - Russia, China, Germany, Britain and France - have all said they want to preserve the agreement that curbed Iran’s nuclear program in return for the lifting of most international sanctions.