(Adds Kerry comments on Iran talks, background on Israeli election)
By Lesley Wroughton
SHARM EL-SHEIK, Egypt, March 14 (Reuters) - On the eve of fresh talks with Iran, U.S. Secretary of State John Kerry said it was unclear whether an interim agreement over its nuclear power program was within reach.
"I can't tell you whether or not we can get a deal, whether we are close," Kerry told a news conference on Saturday in the Red Sea resort of Sharm el-Sheik, where he attended an Egyptian investment summit.
"The purpose of these negotiations is not just to get a deal, it is to get the right deal," he added.
The United States and five other major powers -- Britain, Germany, France, China and Russia -- will resume negotiations with Iran in Lausanne, Switzerland, from Sunday. They hope to clinch a framework agreement by the end of the month.
The two sides would then seek to negotiate by June 30 a final agreement to would curb Iran's most sensitive nuclear activities for at least 10 years. In exchange, sanctions on the Islamic Republic would gradually end.
Kerry expressed concern again that a letter to Iran last week from Republican senators may have undermined the talks. The letter warned Iran that any deal made by President Barack Obama might last only as long as he remained in office -- a highly unusual intervention in U.S. foreign policy-making.
Kerry said he would assure Iranian negotiators and Europeans allies during the upcoming talks that Congress did not have the authority to change the deal.
"As far as we're concerned, Congress has no ability to change an executive agreement," Kerry said, adding that "important gaps" still remained between the sides.
The letter followed a speech to Congress earlier this month by Israeli Prime Minister Benjamin Netanyahu, who warned that Obama was negotiating a "bad deal" with Iran. Republicans invited Netanyahu to speak about Iran without consulting the White House or Democrats.
MIDDLE EAST PEACE PROCESS
With Israel preparing to elect a new government next week, Kerry said the United States hoped that whatever the outcome it would help push forward the peace process with Palestinians.
Opinion polls show Israel's center-left opposition is poised for an upset victory in the parliamentary elections over Prime Minister Benjamin Netanyahu's party.
"President Obama remains committed to a two-state solution," Kerry said, adding "he remains hopeful that whatever choice that people of Israel make, that there will be an ability to be able to move forward on those efforts."
He declined to elaborate on the prospects of resuming the talks, with an election just days away.
Peace talks broke down in April 2014 after nine months of negotiations led by Kerry, with the long-standing goal of a two-state solution no closer.
Kerry met with Palestinian President Mahmoud Abbas on Saturday on the sidelines of the investment conference in Sharm el-Sheik. The meeting included Jordan's King Abdullah and Egyptian President Abdel Fattah al-Sisi.
Abbas has steered clear of taking a position on the Israeli election, saying only that he was ready to work with who wins. (Reporting by Lesley Wroughton; Editing by Larry King)