"Lavrov will meet Steinmeier for a working lunch, afterwards he has a meeting planned with Mogherini," the source told Sputnik.
According to the source, Lavrov will leave Lausanne in the evening. The minister may return Tuesday if the P5+1 group reaches an agreement, the source said.
Earlier on Monday, Lavrov held bilateral meetings with US Secretary of State John Kerry, Chinese Foreign Minister Wang Yi and Iranian Foreign Minister Mohammad Javad Zarif.
All the meetings are held on the sidelines of talks between Iran and the P5+1 group of international mediators, comprising the United States, the United Kingdom, France, China, Russia and Germany.
The goal of the negotiations is to work out a framework agreement by March 31 ahead of an overall agreement expected in June.
The UN Security Council and a number of countries have imposed several rounds of sanctions on Iran, accusing the country of developing nuclear weapons. Tehran has repeatedly rejected those claims, stating that its uranium enrichment program is for peaceful energy purposes only.