"Foreign Minister Steinmeier will not make his planned visit to the... Baltic countries in view of the ongoing talks on the Iranian nuclear programme here in Lausanne," the source said as negotiators took a break after working through the night.
The members of the United Nations Security Council plus Germany are negotiating with Iran on its development of nuclear technology.
The so-called P5+1 hope to persuade Iran to limit the number of centrifuges it has in use and to control the amount of enriched uranium in its possession - effectively curtailing its ability to develop a nuclear bomb - in return for lifting sanctions which have been in place since 2006.
The talks have now been going on for a week. Although rumours emanating from certain diplomatic circles suggest an agreement is close, the original March 31st deadline has been abandoned.