Amid mounting tensions with Iran, acting Defense Secretary Patrick Shanahan announced the U.S. is sending an additional 1,000 troops to the region in a defensive capacity. The Pentagon released new images Monday it says prove that Iran is responsible for last Thursday’s attack on two tankers in the Gulf of Oman. The U.S. military says the images show members of Iran’s Revolutionary Guard removing an unexploded mine from one of the ships. Iran has denied involvement in the attack and some of the U.S. claims have been directly contradicted by the Japanese owner of one of the tankers.

Secretary of State Mike Pompeo has said the U.S. is considering a full range of options following the attack. Republican Senator Tom Cotton, a member of the Armed Services Committee and a Trump ally, called Sunday for a “retaliatory strike” on Iran, saying on CBS’s “Face the Nation,” “The president has the authorization to act to defend American interests.” Neither of the tankers were U.S.-owned; one belonged to a Norwegian company and the other to a Japanese company. The European Union’s foreign policy chief Federica Mogherini called for “maximum restraint” as she heads to D.C. for talks today with U.S. officials. U.N. Secretary-General António Guterres warned last week that the world “cannot afford” a confrontation in the region and that “facts must be established, and responsibilities clarified.”

On Monday, Iran’s atomic energy agency announced it is just days away from reaching the limit of enriched uranium stockpile permitted under the 2015 Iran nuclear deal. The move, according to Iranian officials, is designed to pressure European nations to take more decisive action to maintain the nuclear pact despite the U.S.’s withdrawal last year. Iran said they are still committed to the deal, and have stated repeatedly they are not seeking war with the U.S.