Three US Democratic senators have publicly voiced support for a nuclear conclusion between Iran and the global powers, which has to be approved by the US Congress.

Sen. Bill Nelson (D-Fla.) was last one Tuesday who threw his support behind efforts by the administration of US President Barack Obama to negotiate a nuclear conclusion with Tehran, the Hill reported.

"I acknowledge that this had been one of the most important preparations and will be one of the most important votes that I will cast in the Senate," said Nelson (seen below). "Unless there is an unexpected change in the conditions and facts before the vote is called in September — and it will be called on the very first day that we return in September — unless there is an unexpected change, I will support the nuclear agreement."

He further noted that there is "no other available alternative" for Iran’s nuclear issue.

Since the Republicans are in need of at least 13 Senate Democrats to join their campaign against the agreement, Nelson was one of the dozens who was expected to face pressure to buck Obama.

Improving global security

Earlier in the day, Sens. Tim Kaine (D-Va.) and Barbara Boxer (D-Calif.) also came out in support of the agreement, dubbed Join Comprehensive Plan of Action (JCPOA).

Kaine (seen below) called JCPOA “a dramatic improvement over the status quo in improving global security for at least 15 years and likely longer.”

"In this deal, America has honored its best traditions and shown that patient diplomacy can achieve what isolation and hostility cannot. For this reason, I will support it," said the Virginia senator, who is a member of the Foreign Relations Committee.

JCPOA in best interest of US

The California senator also voiced support for the agreement reached after months of tough negotiations between Iran and the P5+1 – the US, Britain, Russia, China, France, and Germany – in Vienna on July 14.

Boxer (seen below) said she had been “convinced” to back the agreement after talking with diplomats from the United Kingdom, France, and Germany.

She said Iran "now has enough nuclear material to build ten bombs" but "in my view, this agreement is the only way to ensure that Iran's nuclear program is used exclusively for civilian purposes, which is in the best interest of the United States, Israel and the world."

Iran has always said that it is pursuing nuclear energy solely for peaceful purposes.

"The strong support from the international community — including the announcement this week by the (Persian) Gulf states — underscores how this deal is the only viable alternative to war with Iran," she said.

"A deal by definition is never perfect, but as Ami Ayalon, the former head of Shin Bet, Israel's internal security service, said recently, 'When it comes to Iran's nuclear capability, this is the best option,'" she said.

The White House would need to retain support from at least 34 Senate Democrats if Obama is supposed to veto a resolution disapproving the agreement.

The Republican Party members, including the presidential hopefuls, have criticized the outcome of talks with Iran.

Jeb Bush has called it a "terrible deal" while Marco Rubio labeled it "a dangerous and destabilizing failure."

Rick Perry has also pledged to kill the agreement as "one of my first official acts" as president.

Under the agreement, restrictions will be put on Iran’s nuclear activities in exchange for, among other things, the removal of all economic and financial bans against the Islamic Republic.