ISLAMABAD/DUBAI, April 14 (Reuters) - Negotiating teams from the U.S. and Iran could return to Islamabad this week, four sources said on Tuesday, days after the highest-level talks between the two countries since the 1979 Islamic Revolution ended in the Pakistani capital without a breakthrough.

(Reporting by Ariba Shahid in Islamabad, Mubasher Bukhari in Lahore and Hafisa Paresi in Dubai; Editing by Himani Sarkar)