* Obama says deal cuts off "Iran's most likely paths to a bomb"
* Republican senators pour scorn on agreement
* President to call Israeli PM, U.S. official says (Adds Obama plans to talk to Netanyahu)
By Steve Holland and Patricia Zengerle
WASHINGTON, Nov 23 (Reuters) - U.S. President Barack Obama said on Saturday a deal between Iran and world powers was a big step toward a comprehensive solution on Tehran's nuclear program as he tried to win over critics in the U.S. Congress and Israel.
A senior U.S. official said Obama planned to call Israeli Prime Minister Benjamin Netanyahu on Sunday to try to assuage Israeli concerns about the agreement.
"There are substantial limitations which will help prevent Iran from building a nuclear weapon," Obama said in a late-night appearance at the White House after the deal was sealed in Geneva. "Simply put, they cut off Iran's most likely paths to a bomb."
Some of the initial reaction from members of Congress reflected a willingness to take a look at the agreement after weeks of criticism from lawmakers as well as U.S. allies Israel and Saudi Arabia.
Influential Republican Senator Lindsey Graham said on CNN that Congress would likely hold off on new sanctions for six months if Iran sticks to its part of the deal.
"I think you'll see the Congress impose additional sanctions, it won't take place for six months with some conditions. If Iran meets certain conditions they will never go into effect at all," Graham said.
The West fears that Iran has been seeking to develop a nuclear weapons capability. The Islamic Republic denies that, saying its nuclear program is a peaceful energy project.
Democrat Representative Eliot Engel, the top Democrat on House of Representatives Foreign Affairs Committee, expressed concern about the deal. He was a lead co-sponsor of the new Iran sanctions act that passed the House on July 31 and has not yet been taken up in the Senate.
"While I am concerned that this interim agreement does not require Iran to completely halt its enrichment efforts or dismantle its centrifuges, I hope that over the next six months, Iran takes the necessary steps to finally end its quest for a nuclear weapons capability," he said.
Republican Representative Ed Royce, chairman of the House Foreign Affairs Committee, said he had serious concerns that the agreement did not meet the standards necessary to protect the United States.
"Instead of rolling back Iran's program, Tehran would be able to keep the key elements of its nuclear weapons-making capability," he said.
The senior U.S. official who briefed reporters said the Obama administration and lawmakers and Israel all shared the same goal of preventing Iran from developing a nuclear weapon.