Mohammad Javad Zarif's remarks came after a senior US official said a series of secret meetings between Iranian and American envoys had taken place since the June election of President Hassan Rouhani in preparation for Sunday's nuclear deal.
"Our discussions have been limited to the nuclear issue," Zarif said in English when asked about the revelation, without directly commenting on them or giving any details.
"All the speculations about discussions involving other issues are flatly wrong, as we've only concentrated on the nuclear issue," he said.
Iran and the United States broke diplomatic ties following the 1979 hostage taking of American diplomats in Tehran, and have weathered rising tensions in recent years over a number of issues.
Any decision on contacts with Washington, or eventual thaw in relations, rests in the hands of Iran's ultimate authority, supreme leader Ayatollah Ali Khamenei.
Zarif met face-to-face for an hour with his US counterpart John Kerry in New York in late September, the first such meeting since the 1979 Islamic revolution in Iran.
"In discussions on the sidelines of the P5+1 there were various countries, including the United States," Zarif said.
"We made it very clear that there is no problem for Iran to discuss with all the parties... On the resolution of the nuclear issue."
After the agreement was reached Sunday, a senior US official said contacts with Iran were established and series of meetings to "reinforce and ultimately to being part of the P5+1 negotiations."
Zarif did not directly comment on these reports.
