The US is mindful of Iran's missile programme advancing in recent years, the Pentagon has said.
The programme is a threat to US interests, spokesman John Kirby said, but declined to comment on intelligence assessments about the possibility of an Iranian missile launch.
He made the comments against the backdrop of nuclear talks in Vienna between the US, the EU and Iran.
Tehran has made it clear its missile programme is not up for discussion in the nuclear negotiations. In August, newly inaugurated President Ebrahim Raisi gave a speech in which he outlined Iran's stance in any negotiations.
He said while he would negotiate for the relief of sanctions, he would not negotiate over limiting Tehran’s ballistic missile programme or its support for regional militia proxy forces.
Iran's conventional ballistic missile programme is seen as a red line in talks.
Since the Islamic Revolution in 1979, Iran's military aircraft have become obsolete, having been bought prior to the revolution and the Iran-Iraq war.
Many have fallen into disrepair, a problem worsened by sanctions, which has limited Tehran's ability to maintain the aircraft.
In lieu of an effective air force, the government spent billions of dollars over the past few decades building up a missile programme.
Last week, Israeli Defence Minister Benny Gantz said he told US officials a deadline had been given to complete preparations for an attack against Iran.
Israel has been one of the loudest opponents of the Iran nuclear accord, previously pushing the Trump administration to exit the deal unilaterally, causing it to collapse.
Since the Biden administration took office, Israel has made an effort to push the US and Europe to include curbs not just on Iran's nuclear programmes but also on Iran's missile programme.
A source allegedly close to Mr Gantz told Israeli media the US voiced no opposition to the plan and that there was "no veto".
