Criticism of the Iran nuclear deal is certainly fair and warranted.

Criticism without offering an alternative solution is not.

That’s our main problem with those in Congress and elsewhere who have voiced their opposition to the nuclear weapons deal, which will be put to a vote in Washington next month.

Criticism from Republican legislators was expected, but in the past week President Barack Obama has lost support for the deal from several key Democrats in Congress.

Florida Rep. Ted Deutch, in an explanation first voiced in the Sun Sentinel last week, said “Too many issues I have long raised as essential to any nuclear deal with Iran are not adequately raised in this agreement. I will vote against it when Congress reconvenes in September.”

Shortly thereafter, New York Democratic Sen. Chuck Schumer — the presumptive next Democratic leader of the Senate — said he decided against the deal “not because I believe war is a viable or desirable option, nor to challenge the path of diplomacy. It is because I believe Iran will not change .”

On the same day Schumer announced his intentions, New York Rep. Eliot Engel, the ranking Democrat on the House Foreign Affairs Committee, announced his opposition.

And, of course, Israeli Prime Minister Benjamin Netanyahu and others in Israel are vehemently against the deal, knowing that Iran is a sworn enemy of that state.

We respect those who have legitimate concerns on an issue of great importance to the United States and the rest of the world. Reasonable people can disagree and will ignore the insulting arguments of people like presidential hopeful Mike Huckabee, who said the deal will take Israelis to “the door of the oven.”

Even Obama has toned down his rhetoric against critics. He admitted this week there are “absolutely” legitimate concerns about the agreement with a nation that doesn’t exactly inspire anyone’s trust, particularly when it comes to something like nuclear weapons.

But those who oppose the deal need to answer this question — If not this nuclear agreement, then what?

The deal, which has been in the making for over a decade, is surely far from perfect. But bombing Iran’s nuclear facilities, and risking war and overall chaos in the Middle East, is not an option.

Tightening the sanctions on Iran is hardly a guarantee that the country won’t get nuclear weapons. According to USA Today, ambassadors from Britain and Germany warned that if the deal is killed in Congress and can survive Obama’s veto — highly unlikely — international support for sanctions would probably come apart.

The bottom line is there are no ironclad guarantees when you are dealing with Iran. But the deal will dramatically reduce the number of centrifuges, which enrich uranium. For 15 years, Iran will not enrich uranium above the 3.67 percent level needed for nuclear power. According to various reports, right now Iran could possibly produce enough weapons-grade uranium to fuel a single nuclear warhead within two months. The deal would extend that time to about one year.

As far as verification goes, International Atomic Energy Agency inspectors will have access to Iran’s nuclear facilities. A former IAEA inspector, Thomas Shea, called the agreement “a stunning accomplishment.”

Of course there is danger involved. There is a great danger if nothing is done.

With no reasonable alternatives, this is a deal we need to take.