(Reuters) - Iran will have to make further concessions to clinch an agreement on its nuclear program, British Foreign Secretary Philip Hammond said on Monday, adding many difficult issues remained unresolved.

Speaking in Riyadh after talks with Saudi Foreign Minister Saud al-Faisal, Hammond told reporters that while significant progress had been made in talks between Iran and major powers in recent weeks, reaching a deal would be extremely challenging.

"It remains the case that Iran has to make significant further movement if we are going to be able to secure an agreement," Hammond said.

"There are a lot of complex and difficult issues that remain to be resolved before a deal can be agreed. Reaching a comprehensive, lasting and verifiable deal will be extremely challenging but remains in all our interests."

China, Russia, the United States, Germany, France and Britain are trying to reach a framework deal with Tehran by the end of the month that would restrict the most sensitive aspects of Iran's atomic program in return for an easing of international sanctions.

Iran denies that it wants to acquire nuclear weapons.

Hammond said he had assured Saudi authorities that Britain would not accept a deal at any price.

"The right deal is one that allows Iran to have a civilian nuclear program but prevents it from developing a nuclear weapon capability. It remains our position that no deal is better than a bad deal," he said.

By Reuters