* Iran to meet P5+1 in Kazakhstan on Feb. 26
* Obama: World powers united in preventing Iranian bomb
* Tehran has refused to suspend nuclear enrichment (Adds quote)
By Louis Charbonneau
UNITED NATIONS, Feb 13 (Reuters) - European Union foreign policy chief Catherine Ashton urged Iran on Wednesday to show flexibility at this month's talks between Tehran and six world powers aimed at defusing tensions over the Iranian nuclear program.
The five permanent U.N. Security Council members - the United States, Britain, France, Russia and China - and Germany will meet with Iran in Kazakhstan on Feb. 26 for the latest round of talks in a 7-year-old attempt by the so-called P5-plus-one to end the decade-long nuclear standoff with Tehran.
"We hope that Iran will come to this negotiation with flexibility and that we can make substantial progress," Ashton told the 15-nation Security Council during a meeting on the United Nations' cooperation with regional organizations.
"We're engaging in intensive diplomatic efforts to seek a negotiated solution that meets the international community's concern about the Iranian nuclear program," she said.
Ashton has been taking part in and coordinating the six powers' fitful negotiations with Iran.
The Islamic Republic has faced four rounds of U.N. sanctions and more draconian EU and U.S. sanctions due to its refusal to halt its enrichment program as demanded by the Security Council.
"There is no doubt that the pressure of sanctions has been instrumental in bringing Iran back to the negotiating table," she said. "But sanctions cannot be an end in themselves. The key is for Iran to comply fully with its international obligations."
Iran denies that it is seeking a weapon and says its nuclear program serves only peaceful purposes such as electricity generation and the production of medical isotopes.
In his annual State of the Union address, U.S. President Barack Obama said world powers were united in their desire to use diplomacy to prevent Iran from developing atomic weapons, though he left a door open to non-diplomatic avenues like force.
"The leaders of Iran must recognize that now is the time for a diplomatic solution, because a coalition stands united in demanding that they meet their obligations, and we will do what is necessary to prevent them from getting a nuclear weapon," Obama said on Tuesday.
U.S. Secretary of State John Kerry said last week that the six powers were ready to respond if Iran came to the talks prepared to discuss "real substance."
Iranian Foreign Minister Ali Akbar Salehi has said Iran was "counting on there being positive and constructive steps made to resolve this problem at the upcoming meeting."
So far, Iran has refused to suspend its nuclear enrichment program, which the United States, EU and their allies suspect is aimed at producing fuel for weapons. Iran says enrichment is a sovereign right under the nuclear Non-Proliferation Treaty and demanding a halt to the program illegal. (Editing by Doina Chiacu)