US Secretary of State John Kerry called his Iranian counterpart on Wednesday to protest Tehran’s latest round of ballistic missile tests.

US Secretary of State John Kerry called his Iranian counterpart on Wednesday to protest Tehran's latest round of ballistic missile tests.

Iran and the United States have no formal diplomatic ties, but Kerry and Foreign Minister Mohammad Javad Zarif built a close working relationship during negotiations for last year's nuclear accord between Tehran and world powers.

The United States argues that a series of apparent missile tests breach the terms of a UN Security Council resolution and will result in new economic sanctions - either from Washington or the world body.

"If they are confirmed, if they're true, as I said yesterday, we'll take up the appropriate action inside the UN," State Department spokesman John Kirby warned.

"But I don't want to convey the impression that we are only looking at multilateral or UN possibilities in terms of measures to deal with it."