The meeting between representatives of the United States, Iran and the mediating countries of Qatar and Pakistan is still set to take place on Friday, Switzerland's foreign ministry said on Thursday.
The talks are expected to cover initial negotiations on implementing the framework agreement that both sides have already signed, a spokesman told dpa.
The situation is highly dynamic and plans could still change at any time, he added. As of now, the meeting was planned at the Bürgenstock resort, which is owned by Qatar, and is located near Lucerne.
The US-Iran framework agreement entered into force with "immediate effect" overnight, Pakistan said in the early hours of Thursday. The agreement allows for the opening of the Strait of Hormuz and an end to the US naval blockade.
The US says it wants to grant exemptions for Iranian crude oil exports and release Iranian assets abroad. A final agreement, including on the dispute over Iran's controversial nuclear programme, is to be reached in further negotiations within 60 days.
