By Justyna Pawlak BRUSSELS (Reuters) - World powers believe there are enough grounds to keep talking to Iran about its disputed nuclear programme, a senior Western diplomat said on Monday, even though the latest round of negotiations made little apparent progress. "There is enough substance for these negotiations to continue," the diplomat, speaking on condition of anonymity, told reporters. "I would not expect a breakdown."

The United States' top diplomat warned Iran on Sunday that time is running out on nuclear negotiations between the Islamic republic and world powers. "This is not an endless process. ... You can't just talk for the sake of talking," Secretary of State John Kerry told a news conference in Istanbul. Iran and six world powers -- the United States, Russia, China, Britain, France and Germany -- have failed to break the deadlock over Tehran's nuclear drive.

Israel's strategic affairs minister on Sunday called on the international community to slap Iran with a firm ultimatum of "a few weeks, a month" to stop enriching uranium or face a possible military strike. Speaking to army radio, Yuval Steinitz, who also holds the intelligence portfolio, said the latest inconclusive round of nuclear talks between Iran and world powers proved that the Islamic republic was stalling. "The Iranians are playing games and laughing all the way to the bomb," he said.

Iran and world powers Saturday battled to break the deadlock in the crisis over Tehran's nuclear drive, extending talks into the evening after a day of exhausting diplomacy. Officials from both sides were tight-lipped over whether any progress had been made in the talks in Kazakhstan but discussions continued longer than expected. So far the discussions have failed to resolve the main issue of whether Iran will accept limits on its nuclear programme in return for some relief on the sanctions that have hurt the Islamic republic's economy in the past two years.