Andrew Harnik, Associated Press
Joint Chiefs Chairman Gen. Martin Dempsey, right, accompanied by, from left, Secretary of State John Kerry, Treasury Secretary Jacob Lew, Defense Secretary Ash Carter, and Energy Secretary Ernest Moniz, testifies on Capitol Hill in Washington, Wednesday, July 29, 2015, before the Senate Armed Services Committee hearing on the impacts of the Joint Comprehensive Plan of Action (JCPOA) on U.S. Interests and the Military Balance in the Middle East.

WASHINGTON — America's top military leader said Wednesday that the recently signed nuclear deal works to keep Iran from having an atomic weapon, but does not address other concerns about Tehran's malign activities in the region.

"These run the gamut from ballistic missile technology to weapons trafficking, to the use of surrogates and proxies to naval mines and undersea activity — and last but not least to malicious activity in cyberspace," Army Gen. Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, told the Senate Armed Services Committee.

"Ultimately, time and Iranian behavior will determine if the nuclear agreement is effective and sustainable," he said, adding that he will continue to provide President Barack Obama with military options and will advise against reducing U.S. military force presence in the Middle East.

Obama, his Cabinet and other allies are making the case that the deal, which calls on Iran to curb its nuclear program in exchange for billions of dollars in sanctions relief, is the best possible way to prevent Tehran from developing a nuclear weapon.

In addition to Dempsey, Secretary of State John Kerry, Defense Secretary Ash Carter, Energy Secretary Ernest Moniz and Treasury Secretary Jacob Lew testified before the Senate Armed Services Committee.

Congress has begun a 60-day review of the international agreement, with a vote expected in September. If the Republican-controlled Congress passes a resolution of disapproval for the deal, Obama has said he will veto it. The administration is hoping to secure the backing of Democrats to sustain the veto.

At a breakfast with reporters before the hearing, Lew said he believed the White House would gain enough support in Congress to sustain a veto if Congress votes to reject the Iran nuclear deal.

Asked how confident he was that the administration would have the votes to uphold a presidential veto, Lew said he believed there would be sufficient support, "enough for this to be sustained" if Congress does reject the agreement and Obama vetoes the resolution.

Kerry, the lead negotiator of the deal, tried to allay the concerns of Republican senators who complain that they are being asked to vote on the Iran nuclear deal without being privy to verification documents being separately negotiated by international nuclear inspectors.

Sen. John McCain, the chairman of the Senate Armed Services Committee, and other GOP lawmakers say they are being asked to vote on whether to approve or disapprove of the deal before these documents are finalized.

"That is absolutely astounding," McCain said. Iran has a "clear record of cheating."

Kerry said there are no side nor secret agreements between Iran and the International Atomic Energy Agency — that they are technical documents that are standard practice and not released publicly.

"We are aware of what the basics of it are," Kerry told the committee members. "It is standard procedure for 189 counties that have an agreement with the IAEA. ... We don't get that. It is not shared with the world, but we do get briefed on it."

The Iran nuclear deal has supercharged congressional lobbying, with President Barack Obama securing the support of a prominent Jewish Democrat and pro-Israel groups pressuring lawmakers in an all-out, big-money drive.

Nicholas Burns, former undersecretary of state for political affairs and ambassador to NATO, will meet with House Democrats at the invitation of Minority Leader Nancy Pelosi, D-Calif., who is leading the effort to round up Democratic support for the deal. House Democrats also were scheduled to meet with Obama at the White House later in the day.

"I believe that Israel, the region, and the world are far more secure if Iran does not move toward possession of a nuclear weapon," longtime Rep. Sander Levin, D-Mich., said in a statement that referenced his Jewish faith.

On the other side is the powerful American Israel Public Affairs Committee, which is spending millions of dollars on ads to convince lawmakers that Iran can't be trusted and the deal should be scuttled. Its members were personally pressing the argument in meetings on Capitol Hill.

Vote counters are especially focused on members such as Reps. Debbie Wasserman Schultz, D-Fla., and Rep. Steve Israel, D-N.Y., who have not announced how they'll vote. Also undeclared is the House's chief Democratic vote counter, Rep. Steny Hoyer, D-Md.