Iran and world powers expect to announce an initial deal as early as Friday to freeze Iran's nuclear program in return for a letup of sanctions, diplomats said. Secretary of State John Kerry is to travel to Geneva, Switzerland, in the hope of completing the deal with Iranian Foreign Minister Mohammad Javad Zarif, the State Department said. "We are asking them to step up and provide a complete freeze over where they are today," Kerry said Thursday in Amman, Jordan. "Iran knows that if they don't meet the standards of the international community, the sanctions could be increased and even worse," he said. If an agreement is reached, the two could announce the deal by the end of the day, Zarif said. "There is a window of opportunity now that ... needs to be seized," the Iranian envoy told CNN. The two sides were jointly preparing a draft agreement ahead of a likely announcement, The Wall Street Journal reported. President Barack Obama told NBC News Thursday the emerging agreement, part of a "multi-stage" deal, would provide "very modest relief" in economic sanctions in the first six-month phase but would keep the broader "sanctions architecture" and core sanctions in place as a threat if Tehran doesn't comply. "We can crank that [sanctions] dial back up" if Iran doesn't take the deal seriously. The goal is to freeze Iran's nuclear program during the first six-month stage to create breathing room for a comprehensive agreement to be negotiated, said diplomats associated with the negotiations between Iran and the five permanent U.N. Security Council members -- the United States, Russia, China, Britain and France -- and Germany. A U.S. Senate aide briefed by the White House, State Department and diplomats in Geneva told British newspaper The Telegraph the proposed deal had four major points: -- Iran would stop enriching uranium to the 20 percent level that is close to weapons grade and would turn its existing supply of this material into a harmless oxide. -- The country would be allowed to enrich uranium to the 3.5 percent purity needed for nuclear power stations, but would have to limit the number of centrifuges used for this purpose. It would not have to remove or disable any centrifuges. -- Iran would agree not to activate its plutonium reactor at Arak, a city 185 miles southwest of Tehran, during the six-month period. But the country would be allowed to continue developing the facility. -- Iran would agree not to use advanced centrifuges that can enrich uranium up to five times faster than the existing, older model. In exchange for these agreements, Washington would ease some of the crippling financial sanctions they have imposed over the past five years, diplomats said. A senior Obama administration official stressed to the Telegraph only "reversible" sanctions would be eased -- ones that could be reimposed if Iran were to break any deal. Israeli Prime Minister Binyamin Netanyahu criticized the possible deal, saying it would not remove Iran's nuclear capacity, a key Israeli demand. "The proposal would allow Iran to retain the capabilities to make nuclear weapons. Israel totally opposes these proposals," he said. "I believe that adopting them is a mistake of historic proportions." Zarif has repeatedly said Tehran will not give up its "right" to enrich uranium.