The historic accord to close off Iran’s pathways to a nuclear bomb is an enormous win for U.S. national security and President Obama. In the coming weeks, I plan to vote in support of this landmark achievement and urge my colleagues to do the same.

I witnessed firsthand the transformative power of diplomacy as ambassador to Switzerland and Liechtenstein. I commend our diplomats for skillfully averting a global showdown with Iran as part of a deal that blocks its efforts to obtain a nuclear weapon. 

Thanks to the Obama administration’s negotiations, Iran’s nuclear program will be under lock, key and camera 24 hours a day, 365 days a year. The eyes of the international community are on every centrifuge, every ounce of uranium, in all of Iran’s nuclear facilities. Inspectors have “when needed, where needed” inspection rights to any Iranian military site suspected of being involved in the nuclear program.

During my tenure as ambassador to Switzerland, Iran demanded a good deal of my attention. Switzerland has a unique role in our relationship with Iran and in this debate, as the Swiss government has served as the “protecting power” of the United States. Because we have not had formalized diplomatic relations with Iran since 1980, Switzerland represents Washington’s interests in Tehran.

In more recent years, Switzerland regularly hosted negotiations between Iran and the so-called P5+1 countries and Germany. Diplomats from these six world powers concluded the primary agreement with Iran, known as the Joint Plan of Action (JPOA), in Geneva in November 2013.

We can already see the stunning successes of this preliminary agreement. Under the JPOA, the number of inspectors on the ground monitoring Iran’s nuclear sites nearly doubled. Our diplomats have done more to restrain Iran’s nuclear program in the last two years than we saw in the previous two decades when the Iranian nuclear program continued to expand unchecked.

The deal reached in Vienna goes much, much further. Iran will no longer be able to make any uranium or plutonium for a bomb. Iran agrees to rip out a critical two-thirds of its centrifuges under this comprehensive agreement. Sanctions will only be lifted after international inspections verify that Iran is in full compliance. If Iran were to cheat, sanctions will snap back into place. And even if Iran fulfills all of its nuclear commitments, U.S. sanctions on Iranian sponsored terrorism, human rights abuses and ballistic missiles would remain in place.

Contrary to a common erroneous claim, this is no 10-year deal. Col. Richard Klass, a combat veteran of the U.S. Air Force and vice chairman of the Center for Arms Control and Non-Proliferation, described the deal as a “carefully crafted series of restrictions with varying timelines that offers the best chance for preventing Iran from accumulating a nuclear arsenal.” The timelines of some of these restrictions will last for a quarter century. 

The deal’s requirement that Iran ratify the additional protocol means that enhanced inspections will be permanent. Under the Nuclear Non-Proliferation Treaty, Iran will never be allowed to build a nuclear weapon.

It is no wonder then that a consistent majority of the American people support this deal. In fact, a large coalition of faith-based groups and grassroots peace and security organizations are urging members of Congress to vote to support a deal, warning that “this will be among the most consequential national security votes taken by Congress since the decision to authorize the invasion of Iraq.”

The overwhelming consensus among non-proliferation and national security experts is that a diplomatic solution to Iran’s nuclear program is the best way to preserve America’s national security interests. Notably, 30 leading non-proliferation experts called the Lausanne framework agreed to this spring that undergirds the Vienna deal a “net-plus for non-proliferation.”

We cannot allow a nuclear Iran. This deal could serve as a lasting deterrent that keeps our men and women in uniform out of another devastating war in the Middle East. Our diplomats have done their duty to forge this agreement. Now it is incumbent upon every member of Congress to ensure this deal goes forward, without obstruction or delay.

Rep. Don Beyer: Why I’ll vote in favor of the Iran nuclear deal - MSNBC