U.S. Ambassador to the United Nations Samantha Power delivers a speech in New Delhi, India, Nov. 20, 2015. Anindito Mukherjee/Reuters

BY Louis Charbonneau and Michelle Nichols

UNITED NATIONS (Reuters) -- The United States is reviewing and seeking to confirm reports that Iran launched a ballistic missile last month in violation of U.N. Security Council resolutions, U.S. Ambassador to the United Nations Samantha Power said on Tuesday.

"The U.S. is conducting a serious review of the reported incident," Power told reporters after a meeting of the Security Council on unrelated issues.

She added that if Washington confirmed the reports that Iran tested a medium-range ballistic missile on Nov. 21 in violation of U.N. resolutions, the United States would bring the issue to the 15-nation council and seek appropriate action.

A Western diplomatic source said last week on condition of anonymity that the test of a Ghadr-110, a spinoff of the Shahab-3 missile, was held near Chabahar, a port city near Iran's border with Pakistan. He said it was a liquid-fueled missile with a 1,900 km (1,180 mile) range and was capable of carrying a nuclear warhead.

All ballistic missile tests by Iran are banned under a 2010 Security Council resolution that remains valid until a nuclear deal between Iran and six world powers is implemented.

Under that deal, reached on July 14, most sanctions on Iran will be lifted in exchange for curbs on its nuclear program. According to a July 20 resolution endorsing that deal, Iran is still "called upon" to refrain from work on ballistic missiles designed to deliver nuclear weapons for up to eight years.

In October, the United States, Britain and France called for the Security Council's Iran sanctions committee to take action over a test by Tehran of a nuclear-capable missile that month that they said violated U.N. sanctions.

So far, no action has been taken by the committee, though Power said council members would be discussing the issue next week. She added that the United States could take unilateral steps against Iran, though Tehran has warned that it would treat any new sanctions as a breach of the nuclear deal.

U.S. Senator Bob Corker, chairman of the Senate Foreign Relations Committee, issued a statement condemning what he described as the lack of response to Iranian missile violations.

"Iran violates U.N. Security Council resolutions because it knows neither this administration nor the U.N. Security Council is likely to take any action," said Corker.

France said it would pay close attention to ensure Iran respects the ban on ballistic missile tests.

(Additional reporting by Dan Williams in Jerusalem, John Irish in Paris and Arshad Mohammed and Patricia Zengerle in Washington; editing by Alistair Bell and Bernard Orr)