The United States opposes a plan by South and North Korea to set up a no-fly zone over their heavily fortified border, Reuters reported, citing two sources familiar with the matter. Washington and Seoul both publicly insist they are on the same page about dealing with Pyongyang. However, there are growing signs of disagreement as South and North Korea forge ahead with plans to defuse military tensions and rebuild economic ties. The military accord, sealed during last month’s summit in Pyongyang, is one of the most concrete agreements between the neighbors this year. US officials have raised concerns that it could undermine defense readiness and comes without substantial progress on denuclearization.