Danny Danon, Israel’s ambassador to the U.N., said in a Twitter message that the international community must not ‘bury its head in the sand in the face of Iranian aggression.’ PHOTO: ZUMA PRESS

WASHINGTON—Iran staged a missile test launch, U.S. officials said Monday, posing a possible violation of United Nations Security Council resolutions and an early challenge to the Trump administration’s campaign pledge to confront Tehran.

U.S. defense officials, who confirmed the test, declined to identify its specific date, location or range. But Israel’s government and U.S. senators demanded Monday that the U.N. impose new financial sanctions on Iran in response.

Iran’s government is believed to have conducted nearly a dozen ballistic-missile tests since a landmark nuclear agreement between world powers and Tehran was implemented a year ago. Although the estimated timing was indefinite, U.S. officials suggested the latest test happened over the weekend.

“Iran again defied #UNSC resolutions with missiles tests,” Israel’s ambassador to the U.N., Danny Danon, said in a Twitter message on Monday. “The international community again [must not] bury its head in the sand in the face of Iranian aggression.”

The White House and State Department said they were investigating the alleged Iranian launch and gauging whether it violated international law.

The U.N.’s language prohibiting Tehran from developing ballistic missiles was softened under the nuclear deal, which was completed in mid-2015. The U.N. resolution now says the Security Council is against Iran developing missiles, but no longer explicitly bans it.

“We’re aware of reports that Iran conducted a medium-range ballistic missile test in recent days,” State Department spokesman Mark Toner said. “We are, however, well aware of and deeply troubled by Iran’s longstanding provocative and irresponsible activities and we call on Iran to cease such provocations.”

A diplomat at Iran’s mission to the U.N. declined to comment on Monday.

President Donald Trump was a sharp critic of the Iran nuclear deal during last year’s campaign and has suggested he may seek to renegotiate its terms. Many of his top national-security aides, including Secretary of Defense Jim Mattis, have said they would seek to aggressively constrain Iran’s military operations in the Persian Gulf and in such countries as Syria and Iraq.

Trump administration officials have played down the possibility of unilaterally scrapping the nuclear deal. But Republicans in Congress have been drafting new sanctions against Iran, particularly targeting its elite military force, the Islamic Revolutionary Guard Corps.

Congressional officials said this new legislation could be imposed as early as March.

Fox News reported the Iranian missile launch on Sunday. The news channel quoted U.S. officials saying a medium-range Iranian ballistic missile flew 600 miles over the weekend before exploding.

The White House announced on Monday that Israeli Prime Minister Benjamin Netanyahu would visit Washington on Feb. 15 for a summit meeting with Mr. Trump. Israeli officials said constraining Tehran and renegotiating the nuclear agreement is the Israeli leader’s No. 1 priority.

“Iranian aggression must not go unanswered,” Netanyahu tweeted on Monday.

—Ben Kesling contributed to this article.

Write to Jay Solomon at jay.solomon@wsj.com