Negotiations to end the deadlock on Iran’s controversial nuclear programme have overrun into 2 April, two days past the deadline set for reaching a political framework agreement.

The US State Department said the talks in Lausanne, Switzerland, ended at 6am in the morning after an all-night session, but would resume later in the morning.

Iran and the P5+1 world powers were aiming to reach an agreement by 31 March, which would limit Iran’s nuclear development programme in exchange for relief from international sanctions on Tehran’s banks and energy sector.

“Negotiations just broke. Will resume again in a few hours,” announced State Department spokeswoman Marie Harf.

The talks have dragged on as the two sides fail to agree on key issues, such as the amount of development Iran can carry out on new centrifuges and how quickly the UN-enforced sanctions would be lifted after a final agreement.

French Foreign Secretary Laurent Fabius has flown back to Lausanne from Paris in the hope of clinching an agreement, while US Secretary of State John Kerry and German Foreign Minister Frank-Walter Steinmeier said they would stay until at least 2 April to attempt to reach a consensus.

The two sides are aiming to reach a political agreement that would serve as an outline for a detailed accord. Iran and the P5+1 are targeting the latter by a deadline of 30 June.

Negotiators have missed two deadlines since the breakthrough interim agreement was reached in November 2013 with several differences remaining after the most recent talks broke down in November last year.

Tehran is pushing for a long-term agreement that will include the lifting of all economic sanctions imposed by the US, EU and UN, which have crippled Iran’s economy in recent years.