US President Barack Obama told a gathering of military veterans Tuesday that hardheaded diplomacy with Iran could avoid the kind of "unnecessary wars" for which they paid the price.

US President Barack Obama told a gathering of military veterans Tuesday that hardheaded diplomacy with Iran could avoid the kind of "unnecessary wars" for which they paid the price.

Obama travelled to Pittsburgh, Pennsylvania in steely mood, and urged the 1.9 million members of the Veterans of Foreign Wars group to give the nuclear deal with Tehran a chance.

He denounced those "chest beating" against the deal and said some of those opposed to it were the same ones who said the Iraq war would take only months.

"We know the consequences of that choice," he said. "And what it cost us in blood and treasure. There is a smarter more responsible way to protect our national security."

Insisting he was no peacenik afraid to deploy the military, Obama said that "real leadership" means not being afraid to negotiate.

On Tuesday, the Obama administration rolled out a Twitter feed and website that White House spokesman Josh Earnest said will be used to "distribute facts, engage online audiences and be used as a forum by those involved in negotiating the agreement."

The Iran deal is seen as a cornerstone of Obama's foreign policy legacy, and the White House has been selling it at home since the historic agreement was reached last week between Iran and the five permanent members of the UN Security Council plus Germany.