The EU urged Iran Thursday to exercise "restraint" after Tehran vowed to build a new uranium enrichment facility in reaction to a UN nuclear watchdog resolution declaring it in breach of its obligations.

"We call on Iran to restore full cooperation with the agency and fully implement its obligations," said EU foreign policy spokesman Anouar El Anouni, as regional tensions flared ahead of weekend nuclear talks between Washington and Tehran.

"We call on Iran to show restraint and avoid any step that would further escalate the situation," he added, in reference to Iran's promise to "significantly" increase enrichment activities.