The U.S. remains open to diplomacy with North Korea, the country's Deputy Secretary of State Stephen Biegun said on Monday, however stressing that it was "hard to envision" circumstances in which another summit could take place before the upcoming U.S. presidential election in November.Speaking in a webinar hosted by the Washington, D.C.-based think tank, the German Marshall Fund, Biegun argued that continued economic pressure on North Korea caused by international sanctions would likely keep Pyongyang interested in talks with the U.S."The hardship in North Korea is palpable," Biegun said. "The pressures are immense