WASHINGTON -- Just hours before the Senate convenes to start the process of voting on the Iran nuclear deal, Minority Leader Harry Reid (D-Nev.) delivered a forceful message for his colleagues: either support the nuclear agreement or allow Iran to build a nuclear weapon.

We can take the strongest step ever toward blocking Iran from getting a nuclear bomb, or we can block this agreement and all but ensure Iran will have the fissile material it would need to make a bomb in a matter of months, Reid said Tuesday, speaking at the Carnegie Endowment for International Peace. We cannot have it both ways.

The current nuclear accord, negotiated in July between Iran, the U.S. and five world powers, is not only the best option the U.S. currently has to block Irans nuclear weapons program, but is likely to the last opportunity to do so, Reid said.

At the time of Reids remarks, 38 Senate Democrats have publicly indicated that they will vote to uphold the nuclear deal, meaning that Senate Republicans will not be able to override a veto by President Barack Obama if they were to reject the accord. Reids speech is part of a final push to get three of the four undecided Democrats to back the agreement and render a presidential veto unnecessary.

Though almost every Senate Republican has pledged to vote down the nuclear accord, Reid noted that Brent Scowcroft, a former national security advisor to two Republican presidents, had recently phrased Congress options in similar terms. The forthcoming vote, Scowcroft wrote in The Washington Post, will show the world whether the United States has the will and sense of responsibility to help stabilize the Middle East, or whether it will contribute to further turmoil, including the possible spread of nuclear weapons.

In his remarks, Reid thanked two of the four Senate Democrats who have strayed from their party and announced they will vote against the Iran deal for their broader efforts in the Iran debate. He acknowledged Sen. Bob Menendez (D-N.J.) for driving the sanctions legislation that some credit with bringing Iran to the negotiating table, and Sen. Ben Cardin (D-Md.) for working with Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) to craft legislation that allowed Congress to weigh in on the nuclear agreement.

The Senate minority leader made no mention of Sen. Chuck Schumer (D-N.Y.) -- the first Democrat to oppose the deal -- who is Reids likely successor as the head of the Senate Democrats.

Reid emphasized his commitment to ensuring that Israel maintains its qualitative military edge in the region and insisted that implementation of the nuclear deal will make Israel safer. He said he had closely reviewed the legislation Cardin proposed, which would allow the U.S. to supply Israel with the bunker-busting Massive Ordnance Penetrator, the 30,000 pound bomb that is, theoretically, the weapon most capable of destroying Irans nuclear facilities if the agreement were to collapse.

Reid did not specify whether he would support Cardins legislation, but it is unlikely the Obama administration will approve the sale of the massive bomb to Israel. As Daryl Kimball of the Arms Control Association noted last week, B-2 or B-52 bombers are the only planes capable of carrying the MOP, and the sale of either plane to Israel would violate U.S. treaty commitments.

The Obama administration has said that it will provide Israel with other penetrating munitions for theoretical use against Iranian nuclear sites, and will sell Israel the F-35 advanced fighter jet long before it becomes available to other regional allies.

While supportive of increased military aid to Israel, Reid reiterated that the diplomatic accord is the most effective way to prevent Irans access to nuclear weapons. In our day, we know it is not practical to bomb away knowledge of how to build a nuclear weapon, he said. Even though we cannot take away the recipe to build a bomb, we can take away both the ingredients and the use of equipment to cook one. Thats what were doing -- but only if the United States upholds and enforces this agreement.