RIYADH/WASHINGTON  - Saudi Foreign Minister Prince Saud al-Faisal said on Monday that Iran, which is negotiating with world powers on its nuclear programme, should not get "undeserved deals". "It is impossible that Iran should get undeserved deals," Prince Saud said at a joint news conference with visiting British Foreign Secretary Philip Hammond.

Iran and six world powers are in negotiations to clinch a long-sought deal aimed at putting a nuclear bomb out of reach for the country in exchange for easing sanctions on its economy. Tehran denies wanting nuclear weapons.

Prince Saud called for guarantees that the programme "does not turn into a nuclear weapon that could pose a threat to the region and the world, especially in view of Iran's aggressive politics in the region". The minister also accused Tehran of "continued meddling in the affairs of Arab countries and attempts to stoke sectarian conflicts in the region".

Tehran has backed Syrian President Bashar al-Assad while Riyadh supported rebels trying to topple him.

Meanwhile, any nuclear accord must constrain Iran's nuclear infrastructure for "decades" before the US Congress will lift sanctions, 80 percent of the House of Representatives told President Barack Obama on Monday. The 367 representatives, Democrats and Republicans, highlighted "grave and urgent" issues in the negotiations between Iran and the P5+1 group of world powers. "A final comprehensive nuclear agreement must constrain Iran's nuclear infrastructure so that Iran has no pathway to a bomb, and that agreement must be long-lasting," said the letter.

The negotiations are supposed to resume Wednesday in Switzerland, ahead of an end-of-the-month deadline for reaching an accord. The P5+1 is made up of Britain, China, France, Russia, the United States and Germany.

"Given Iran's decades of deception, negotiators must obtain maximum commitments to transparency by Iran," the letter said.

"Any inspection and verification regime must allow for short notice access to suspect locations, and verifiable constraints on Iran's nuclear program must last for decades."

For months now, the Congress has been at loggerheads with the Obama administration, with the Republican majority criticizing a deal even before it is struck.

Many Democrats also have said they are skeptical and ready to act, by legislative means, to block any accord that in their view does not sufficiently dismantle Iran's nuclear infrastructure.

A letter to Iran's leaders, signed by almost all Republican senators, set off a furor two weeks ago by warning that Obama did not have the power to conclude a durable agreement with Iran on his own, and insisting that congressional support was indispensable.

In Monday's letter, the House members also warned that permanent sanctions relief would require new legislation.

"In reviewing such an agreement, Congress must be convinced that its terms foreclose any pathway to a bomb, and only then will Congress be able to consider permanent sanctions relief," it said.

Administration officials have swarmed the Congress to reassure lawmakers.

Last week, the State Department's number two, Antony Blinken, offered assurances that any agreement would prevent Iran from building a nuclear weapon, and would be accompanied by a gradual easing of US sanctions.

The Senate Foreign Affairs Committee has scheduled an April 14 meeting to consider a bill that would require consultation with Congress in the event an accord is reached.