WASHINGTON: A trio of Obama administration officials will stand stalwart behind the Iranian nuclear deal despite deep concern on Capitol Hill that Iran will try to evade nuclear inspectors and use billions from sanctions relief to further destabilize the Middle East.

Members of the Senate Foreign Relations Committee on Thursday are to pose tough questions to Secretary of State John Kerry, Energy Secretary Ernest Moniz and Treasury Secretary Jack Lew about the deal that Congress is expected to vote on in September. The three were on Capitol Hill Wednesday for back-to-back classified briefings in the House and the Senate.

A debate is under way between supporters and the opposition, which includes many Jewish groups that point to Iran's pledge to destroy Israel. Vote counters are eyeing Democrats, especially those who represent large Jewish constituencies and likely will be lobbied hard to oppose the deal at home during the August recess.

Most Democrats — except Sen. Dick Durbin of Illinois who announced his support earlier in the week — came out of the classified briefings saying they were still deciding whether to support the agreement, which Congress has 60 days to review.

"I think the deal is a dramatic improvement over the status quo from day 1 through probably year 10 to 15. Thereafter my questions are about our ability to detect cheating after some of the provisions start to expire," said Virginian Democratic Sen. Tim Kaine, who sits on the committee.

"I'd be shocked if there's more than a handful of Republican 'yes' votes if there are any at all," said Sen. Chris Murphy, D-Connecticut. "But I've talked to most all my colleagues on the Democratic side. ... I think the administration is one-by-one picking off some of the most important lingering questions from Democrats."

Murphy, another member of the committee, said he still has questions about whether the inspection protocol will be as rigorous as the administration claims, but that if it is, he'll support the deal.

Most Republicans exited the meetings still opposed.

Sen. Tom Cotton, R-Ark., said: "Iran is a terror-sponsoring anti-American regime. ... This deal is going to give tens of billions of dollars — at a minimum — without doing anything to rein in their support for terror or their support for America's enemies."

Cotton and Rep. Mike Pompeo, R-Kan., wrote a letter to Obama on Wednesday, complaining that the agreement includes two "side deals" the International Atomic Energy Agency was negotiating separately with Iran — issues that the Congress has not been privy to.

State Department spokesman John Kirby said there were no "side" or "secret" agreements between Iran and the IAEA that the United States and the five other world powers have not been briefed on in detail. "These kinds of technical arrangements with the IAEA are as a matter of standard practice not released publicly."

The deal does not need congressional approval to take effect, but Republicans are expected to try and sink it with legislation that would block Obama from lifting sanctions imposed by Congress. The president has vowed to veto any such bill, and it would take a two-thirds majority in each house of the Republican-controlled Congress to override him.