Iran's missile capabilities are a red line and are not subject to negotiations. This was stated by an adviser to Iran's supreme leader, quoted by "Reuters".
Tehran and Washington are considering a new round of talks to prevent conflict.
American and Iranian diplomats held indirect talks last week in Oman, amid a regional US naval buildup threatening Iran.
"The Islamic Republic's missile capabilities are non-negotiable," Ali Shamkhani said at an event marking the 47th anniversary of the Islamic Revolution.
Washington has long sought to expand negotiations on Iran's nuclear capabilities to include its missile program.
Tehran has said it is willing to discuss restrictions on its nuclear program in exchange for the lifting of sanctions, but has repeatedly ruled out linking the issue to other areas, including missiles.
Israeli Prime Minister Is Expected Benjamin Netanyahu is to use a meeting with Trump in Washington today to demand that any potential U.S.-Iran deal include restrictions on Tehran's missiles.
On Sunday, Iranian Foreign Minister Abbas Araqchi said Tehran's missile program was never part of the negotiations' agenda.