Switzerland's Foreign Minister Ignazio Cassis said he had "fruitful" talks in Iran on Monday 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.
Switzerland has also played a major role in prisoner swaps between Tehran and Washington.
Iran-US tensions have escalated since 2018, after President Donald Trump withdrew the US from the Iran nuclear agreement and reimposed tough sanctions on the Islamic republic.
Cassis held talks with his Iranian counterpart Mohammad Javad Zarif before later meeting with President Hassan Rouhani.
The Swiss top diplomat held the meetings as part of a three-day visit to Tehran celebrating a century of diplomatic relations between the two countries.
"Peace, economic development and human rights -- fruitful discussion with my counterpart," Cassis wrote on Twitter after the talks.
Zarif called the talks "excellent" on Twitter and said "while appreciating Swiss efforts to mitigate US sabotage, a return to normal trade is global priority".
Rouhani reiterated that Iran was "open" to the United States to reverse its "mistakes", repair "its illegal actions" and rejoin the nuclear agreement, said state news agency IRNA.
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.
The Swiss channel is a payment mechanism aimed at enabling 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 -- known by its acronym SHTA -- was established and conducted its first transaction earlier this year.