With Iran's nuclear deadline fast-approaching, officials has indicated that negotiators might need more time. The US, Britain, China, France and Germany - known as the P5+1 - want a framework pact with Iran.
Foreign ministers deliberated in Lausanne for what they hoped would be the final day of high-level negotiations with Iran, which the P5+1 hopes will result in a containment of Tehran's nuclear ambitions.
However, with less than six hours until the deadline, White House spokesperson Josh Earnest indicated that talks could extend into Wednesday if they continued to be productive.
"If we are making progress toward the finish line, then we should keep going," Earnest said.
France's foreign minister, Laurent Fabius, also confirmed this, describing the situation as "complicated."
"We are making progress. But...it's long and difficult. And I'm afraid that we may be going through the night," Fabius told reporters.
US Secretary of State John Kerry told US news channel CNN earlier in the day that diplomats faced "difficult issues."
"We are trying very hard to work those through," Kerry said.
The P5+1 is attempting to convince Tehran to curb its nuclear program, which the Iranian government contends is supposed to serve civilian purposes.
However, critics of the talks, such as Israeli Prime Minister Benjamin Netanyahu, have repeatedly warned of nuclear proliferation and the increased potential for an arms race under the terms of the current negotiations.
An final agreement is set to be reached by June 30.
kms/jr (AP, AFP)