The United States has sketched out a path under which three key European allies would simply commit to try to improve the Iran nuclear deal over time in return for President Donald Trump keeping the pact alive by renewing U.S. sanctions relief in May.

The approach, outlined in a State Department cable obtained by Reuters and an interview with a senior department official last week, still faces obstacles. The European allies are uncertain what will satisfy Trump and are reluctant to make such a commitment only to find that he asks them for more, two European officials and two former U.S. officials said.

The cable's characterization of what the United States wants from the Europeans, which has not been previously reported, sets a lower standard than laid out by Trump in January and so might facilitate a meeting of the minds, five current European and four former U.S. officials said.