(Reuters) - U.S. President Donald Trump will make an announcement this week on an "overall Iran strategy," including whether to decertify the international deal curbing Tehran's nuclear program, the White House said on Tuesday.

"He'll make that later this week," White House spokeswoman Sarah Sanders told reporters when asked about the certification decision and the administration's broader strategy on Iran.

Trump, who has called the 2015 pact agreed between Iran and six world powers an "embarrassment," is expected to announce that he will decertify the deal ahead of an Oct. 15 deadline, a senior administration official said last week.

Trump is also expected to designate Iran's most powerful security force, the Islamic Revolutionary Guards Corp, as a terrorist organization as part of a new Iran strategy.

"The president has reached a decision on an overall Iran strategy and wants to make sure that we have a broad policy to deal with ... all of the problems of Iran being a bad actor," Sanders said.

Trump accuses Iran of supporting terrorism and says the 2015 deal does not do enough to block its path to acquire nuclear weapons.

Iran says it does not seek nuclear weapons and in turn blames the growth of militant groups such as Islamic State on the policies of the United States and its regional allies.

The hawkish turn in U.S. policy toward Iran has alarmed many of its European allies. British Prime Minister Theresa May told Trump by phone on Tuesday that the deal was "vitally important for regional security."

German Foreign Minister Sigmar Gabriel on Monday urged the United States "not to call into question such an important achievement that has improved our security."

France voiced concern on Tuesday that designating the Revolutionary Guards a terrorist group could exacerbate tensions in the region. If Trump declines to certify the Iran deal, U.S. congressional leaders would have 60 days to decide whether to reimpose sanctions on Tehran suspended under the agreement.

Iranian authorities, who have said Tehran would not be the first to violate the accord, have stepped up their rhetoric against the Trump administration over the possible terrorist designation of the Revolutionary Guards. "The Americans have driven the world crazy by their behavior. It is time to teach them a new lesson," Iranian armed forces spokesman Masoud Jazayeri said on Tuesday.