Iranian Foreign Minister Abbas Araghchi said it would be "very, very dangerous for everyone" if the US gets actively involved in the war between Iran and Israel, the Associated Press reported.
US President Donald Trump is considering American military involvement, which Araghchi said would be "very unfortunate".
He made the statement to the media in Istanbul on his way back from the Geneva talks, which failed to produce a diplomatic breakthrough.
After the talks ended, Araghchi said he was open to further dialogue, but stressed that Tehran has no interest in negotiating with the US while Israel continues to attack.
Araghchi arrived in Istanbul to attend a meeting of the Organization of Islamic Cooperation (OIC), whose agenda is dominated by the topic of Tehran's ongoing conflict with Israel, DPA recalls.