U.S. lawmakers seek tighter Iran sanctions before any deal

(Releads with U.S. lawmakers, adds Lavrov, Sherman)

* Iran president addresses hardline critics, France, Israel

* Iran, six world powers to resume negotiations Nov. 20

* Kerry says "I don't think we're stupid" in negotiations

* Still prospects for breakthrough deal soon - Britain

By Andy Sullivan and Stephanie Nebehay

WASHINGTON/GENEVA, Nov 10 (Reuters) - U.S. lawmakers said on Sunday they aimed to tighten sanctions on Iran to prevent Washington giving away too much in a deal on Tehran's nuclear programme that diplomats said was still possible despite the failure of high-level weekend talks.

Their comments reflected widespread Congressional scepticism about a rapprochement between Iran and world powers and coincided with renewed lobbying from Israel against a proposal it sees as leaving open a danger Iran could build a nuclear bomb. Tehran denies harbouring any such ambition.

Negotiators from world powers will resume talks with Iran in 10 days after failing late on Saturday to reach agreement on an initial proposal to ease international sanctions against Tehran in return for some restraints on its nuclear programme.

The new talks will be at a lower level than the foreign ministers who gathered in Geneva at the weekend, but Britain and Russia both said the chances for a deal were fairly high.

The sides seemed on the verge of a breakthrough - before cracks materialised among U.S. and European allies as French Foreign Minister Laurent Fabius dismissed the plans as a "fool's game" of one-sided concessions.

The Senate Foreign Relations Committee will move ahead with additional sanctions this week to keep the pressure on Iran as talks continue, said Democratic Senator Bob Menendez, the committee's Democratic chairman.

"My concern here is that we seem to want the deal almost more than the Iranians," Menendez said on ABC's "This Week."

U.S. Secretary of State John Kerry, who joined the Geneva negotiations unexpectedly on Friday to help bridge differences, defended the administration's position.

"We are not blind, and I don't think we're stupid," he said on U.S. television. "I think we have a pretty strong sense of how to measure whether or not we are acting in the interests of our country and of the globe."

IRANIAN "RED LINES"

For his part, Iranian President Hassan Rouhani sought to win hardliners in parliament over to his diplomatic opening to world powers, said it had "red lines".

"We will not answer to any threat, sanction, humiliation or discrimination," was the message Iranian negotiators had told their big power interlocutors in Geneva, Rouhani said.