Senate Minority Whip Dick Durbin said Tuesday he will back the nuclear deal with Iran, becoming the highest ranking Democrat in the chamber to endorse the accord so far.

Durbin, of Illinois, said in a Senate floor speech that the deal goes far to reduce Iran's ability to create a nuclear weapon, and that it includes strong enforcement provisions that will ensure the Islamic nation is keeping up its end of the deal.

"This agreement cuts off every one of Iran's potential avenues to a bomb," Durbin said, adding that the accord requires Iran to cut it uranium enrichment by 98 percent and its centrifuges by two-thirds.

Many Democrats remain undecided about the deal, which was endorsed earlier this week by the United Nations.

Two other Democratic Senate leaders, Minority Leader Harry Reid of Nevada and Charles Schumer of New York, said they are reviewing it and are undecided.

President Obama will need to secure the support of at least a third of each chamber in order to prevent lawmakers from overriding a veto of a resolution of disapproval that is likely to pass with Republican support.

The Obama administration has launched an intensive lobbying effort. Secretary of State John Kerry and other cabinet members will visit the House and Senate beginning Wednesday to sell the deal.

In the House, Minority Leader Nancy Pelosi, D-Calif., is vigorously supporting the legislation and working to convince her rank-and-file to do the same. But the number-two Democrat, Minority Whip Steny Hoyer, D-Md, said Tuesday he remains undecided.

Durbin on Tuesday suggested it was the best deal possible.

"There isn't a single critic who has stepped up with a better idea," Durbin said.