(Recasts with Congress pressuring White House)

By Andy Sullivan

WASHINGTON, Nov 10 (Reuters) - U.S. lawmakers said on Sunday they aim to tighten sanctions on Iran to ensure the Obama administration does not give away too much in a planned deal to stop Tehran's nuclear development program.

The remarks are further evidence of the skepticism the Obama administration faces at home and abroad in its efforts to build a dialogue with the Islamic republic after more than three decades of deep mistrust.

"We know the sanctions have gotten us here and we're worried we're dealing away our leverage," Bob Corker, the top Republican on the Senate Foreign Relations Committee, said on NBC's "Meet the Press."

That 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."

The United States and its allies narrowed their differences with Tehran over the weekend, but were not able to reach a deal as France believed the proposal did not adequately neutralize the risk of an Iranian atom bomb. Iran says its nuclear program is peaceful in nature. The two sides have held two rounds of talks and plan to meet again in Geneva on Nov. 20.

"I've never been more worried about the Obama administration's approach to the Mideast than I am now," Republican Senator Lindsey Graham said on CNN's "State of the Union."

"Thank God for France," he added.

U.S. Secretary of State John Kerry, who participated in the talks, said other countries involved in the talks share France's concerns and the United States would not agree to a deal that it found inadequate. Russia, China, Britain and Germany have also been involved in the negotiations.

"We are not blind, and I don't think we're stupid. 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," Kerry said on NBC's "Meet the Press."

The deal under discussion would freeze Iran's higher-grade uranium enrichment for six months and open up the programme to U.N. anti-proliferation inspectors. During that time, Iran and the six powers would negotiate a permanent agreement aimed at ensuring that none of Iran's nuclear activities could be diverted towards bomb-making.

In exchange, Tehran would obtain phased and initially limited relief from sanctions.

One possible concession would allow Iran access to about $50 billion that has been frozen in foreign accounts for years. Allies could also temporarily relax restrictions on precious metals trading, and Washington could ease pressure on countries not to buy Iranian oil.