Tough talks to reach a framework deal to curtail Iran`s nuclear programme may go past a midnight deadline into Wednesday, a top US official acknowledged.
Diplomats and experts were "working around the clock", the senior State Department official said Tuesday.
"Our team is evaluating where we are throughout the day and making decisions about the best path forward," the official added, asking not to be named.
"We will of course keep working if we are continuing to make progress, including into tomorrow, if it`s useful to do so. At this time, no decisions have been made about our travel schedule."
The announcement that the US team may be seeking to buy more time ahead of a Tuesday`s midnight deadline came as diplomats reported that despite initial high hopes, progress had been slower than desired in the past nail-biting hours.
