The U.S., Iran and five other world powers working on a deal to limit Iran's nuclear program took a several-hour pause to sleep early Thursday after a marathon session that lasted through the night, NBC News reported. Two days beyond the long-standing deadline to reach a deal, the all-night talks were focused on whether the U.S. and EU would agree to ease banking, oil and financial sanctions, apart from United Nations sanctions, officials said. Secretary of State John Kerry is planning to remain in Switzerland for the talks because "we continue to make progress but have not reached a political understanding," according to Marie Harf, the State Department's acting spokeswoman. Iranian Foreign Minister Javad Zarif warned that the window for negotiations was closing, and rejected the "pressure" of international sanctions as a negotiating tactic. "Iran has shown its readiness to engage with dignity, and it's time for our negotiating partners to seize the moment and use this opportunity which may not be repeated," he said.