WASHINGTON (Reuters) - The Obama administration is considering how to respond to an Iranian ballistic missile launch that violated U.N. Security Council resolutions, senior U.S. officials said on Thursday, as senators pressed for a strong reaction.

An Iranian Emad rocket is launched as it is tested at an undisclosed location October 11, 2015. REUTERS/farsnews.com/Handout via Reuters

“We are now actively considering the appropriate consequences to that launch in October,” Stephen Mull, the State Department’s lead coordinator for implementing an international nuclear deal with Iran, told a Senate committee hearing.

Almost every Republican U.S. lawmaker, as well as several of President Barack Obama’s fellow Democrats, opposed the nuclear agreement announced in July, in which Iran agreed with major powers to curtail its nuclear program in exchange for relief from economic sanctions.

Concerns in the United States about the agreement have intensified since Iran’s rocket test on Oct. 10 and other events seen as hostile, including the conviction of Washington Post reporter Jason Rezaian, who has been held by Tehran for more than 500 days.

Many lawmakers criticize the Obama administration for what they see as an inadequate response to Tehran.

“One area that we all agree on is the need to be tough on any destabilizing or illegal action by Iran. With that view, I think the agreement is off to a really terrible start,” said Republican Senator Bob Corker, chairman of the Senate Foreign Relations Committee.

As first reported by Reuters, a team of sanctions monitors in a report on Tuesday found that Iran violated a U.N. Security Council resolution by test-firing a missile capable of delivering a nuclear warhead.

“We have a very permissive environment,” said Democratic Senator Robert Menendez, who opposes the nuclear deal, as he closely questioned Mull and other administration officials about the response to the missile test.

Senator Chris Coons, another Democrat who backed the Iran deal but with reservations, said that starting next month members of Congress would push for renewal of a U.S. sanctions bill that is in force until the end of 2016.

Mull said the administration is looking forward to working with Congress on the issue.

Asked whether he thought Iran would view renewing the legislation as a U.S. violation of the nuclear deal, Mull said it would be hard to predict.

Separately, two-thirds of the Republicans in the Senate signed a letter sent to Obama on Wednesday urging him not to lift sanctions on Iran under the nuclear deal, saying Tehran’s recent ballistic missile testing showed “blatant disregard for its international obligations.”

On Thursday, 21 Democratic senators led by Ben Cardin, the top Democrat on the foreign relations panel, also wrote to Obama, saying they were deeply concerned about Iran’s ballistic missile testing.