In a stinging setback, the United States and South Korea failed to reach agreement on an elusive free-trade deal but will continue pressing for an accord in the weeks ahead, President Barack Obama said Thursday. Obama had hoped to announce a deal on the long-stalled pact while in South Korea for meetings of the Group of 20 economic powers, but instead he will return home empty-handed. "We have asked our teams to work tirelessly in the coming days and weeks to get this completed," Obama said at a joint news conference with South Korean President Lee Myung-bak. "We don't want months to pass before we get this done," Obama said. "We want this to be done in a matter of weeks." Prospects for reaching a deal seemed unlikely before Obama's meeting and subsequent appearance with Lee.