Defense Secretary Jim Mattis, an ardent critic of what he considers Iran's destructive activities in the Middle East, said Tuesday that the Trump administration should not break with the international agreement designed to limit Tehran's nuclear program.

Testifying before the Senate Armed Services Committee, Mattis was asked by Sen. Angus King whether it was in the U.S. national security interest to remain with the deal, known formally as the Joint Comprehensive Plan of Action.

"Yes, Senator, I do," Mattis, after a brief pause, told the Maine independent.

Though the purpose of Tuesday's hearing was to focus on the new Defense Department strategy for Afghanistan – which will involve the deployment of at least 3,000 more troops into America's longest war – lawmakers on the dais probed Mattis and Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, about threats facing the U.S. throughout the Middle East and elsewhere, including on the Korean Peninsula.

President Donald Trump faces an Oct. 15 deadline to determine whether he will once again confirm that Iran remains in compliance with the deal, which he routinely blasted on the campaign trail and continues to say the U.S. should tear up. The U.S. has affirmed Iran's compliance twice since Trump took office.

When asked earlier on Tuesday by Sen. Kirsten Gillibrand about the effect of breaking with the deal, Mattis listed a series of Tehran's provocative moves outside of the agreement, including its development of ballistic missiles, reported support to terrorist groups – including Hamas in the Palestinian territories and Hezbollah in Iran – and threats to U.S. allies like Israel.

"The amount of misconduct, as I would call it," Mattis told the New York Democrat, "are areas where they are open to a great deal of censure by the international community. And we are not being naive about their agreement on the nuclear issue, and we are being very alert to any cheating on that right now."