Iran has to take some "tough decisions" as world powers seek to hammer out a nuclear deal, U.S. Secretary of State John Kerry said Thursday, according to AFP.
His comments came as he was grilled by lawmakers over the talks between Iran and the so-called P5+1 group of world powers, which are due to start up again in Vienna on Monday.
Under a six-month interim deal, Iran agreed to freeze its uranium enrichment program in return for sanctions relief worth some $6-7 billion, including the transfer of some $4.2 billion in frozen overseas funds.
Kerry insisted during a hearing of the Senate appropriations committee that Washington was testing whether the new Iranian leadership of President Hassan Rouhani was serious in reining in its nuclear program, which the West believes is a covert grab for an atomic bomb.
"We believe we're heading in the right direction. I can't tell you where it's going to finally land, we don't know," Kerry said of the negotiations due to last for the next six months towards a comprehensive deal.
"There's some very tough decisions the Iranians are going to have to make -- very tough -- in order to meet the international community's standard for certainty as to the peacefulness of this program," he added, according to AFP.
He hit back against criticism that Iran was now attracting cash-flow and business back to the country, and that the sanctions relief was being used to fund Hezbollah terrorists fighting in Syria.
Kerry said he had contacted his counterparts around the world amid reports of trade delegations going to Iran.
"We have made it crystal clear that Iran is not open for business. They have accepted that," he declared, according to AFP.
"They are not cutting deals. There are people who have traveled, but there have not been new deals."
Last month, Kerry criticized France, after a delegation of French business figures visited Tehran. Kerry had told his French counterpart that the trip, even though organized through the private sector, was “not helpful” in sending the message that “it is not business as usual” with Iran.
France’s Finance Minister rejected the criticism, saying that the 116-person delegation was “a bet” on the future and not “business as usual.”
On Thursday, Kerry stressed again that the tough sanctions regime put in place against Iran had not been dismantled.
"Nothing in the architecture of the sanctions regime has been changed whatsoever. Iran's economy contracted by 6 percent last year. It is expected to contract again this year. Inflation remains at almost 40 percent," Kerry told lawmakers.
He also tussled with Republican Senator Mark Kirk, who suggested that with the sanctions relief Iran now had some $25 billion in liquid assets which it was using to boost payments to Hezbollah.
"I would expect that we would see even more terrorism with this additional money available to the Islamic Republic of Iran," Kirk told Kerry, reported AFP.
Kerry countered that Iran "has huge economic problems" and said around $15 billion to $30 billion of Iran's earnings, mainly from oil revenues, was being siphoned away and frozen in overseas accounts.
"So they're losing. They're losing enormous sums of money and more than a hundred billion dollars that is now frozen," he claimed.
Some American lawmakers have been pushing for stronger measures against Iran even after the deal was reached, despite warnings from the White House that this could scupper the negotiations and lead to a military confrontation with Iran.
President Barack Obama has promised tough action against firms violating sanctions against Iran, saying the U.S. “will come down like a ton of bricks” on any sanctions violators.