Switzerland's Foreign Minister Ignazio Cassis said he had "fruitful" talks on Monday with his Iranian counterpart Mohammad Javad Zarif regarding "peace, economic development and human rights."
The Swiss embassy in Tehran handles US interests in Iran, since ties were cut in the aftermath of the 1979 Islamic revolution.
Cassis is expected to meet President Hassan Rouhani as part of a three-day visit to Tehran, celebrating a century of relations between Switzerland and Iran.
Tensions between Iran and the US have escalated since 2018, after President Donald Trump withdrew the US from an international nuclear agreement and reimposed tough sanctions on Iran.
"Peace, economic development and human rights - fruitful discussion with my counterpart," Cassis wrote on Twitter following the talks.
Switzerland has also played a major role in prisoner swaps between Tehran and Washington.
According to the US Department of State, Secretary Mike Pompeo had a phone call with Cassis before his Tehran visit, raising speculation the visit involved talks on Tehran-Washington relations.
Iran's foreign ministry spokesman Saeed Khatibzadeh denied the "speculations" on Monday, saying it was a planned visit delayed over the novel coronavirus outbreak and "not related to Iran and the US".
"I'm glad we could establish together the Swiss Humanitarian Channel for the transfer of food and medical supplies to the people of Iran," Cassis said on Twitter.
Known by its acronym SHTA, the Swiss channel is a payment mechanism aimed to enable food, medicine and other humanitarian aid to be sent to Iran without breaking US sanctions.
Humanitarian goods are theoretically exempt from sanctions, but international purchases of such supplies are almost impossible since banks are wary of falling foul of the US over doing business with Iran.
The channel was established and conducted its first transaction earlier this year.