Although the Second London Naval Treaty stipulated that warship guns could be no larger than 14 inches, a so-called "escalator clause" was included at the urging of American negotiators in case any country that had signed the Washington Naval Treaty refused to adhere to this new limit. The provision allowed signatory countries of the Second London Treaty—France, the United Kingdom and the United States—to raise the limit from 14 to 16 inches if Japan or Italy still refused to sign after 1 April 1937. When figuring potential configurations for the "North Carolina"s, designers focused most of their planning on 14-inch weaponry; Standley's requirement meant that a switch from 14- to 16-inch, even after the ships' keels had been laid, was possible. Japan formally rejected the 14-inch limit on 27 March 1937, meaning that the "escalator clause" "could" be invoked. There were hurdles that still needed to be overcome, though: Roosevelt was under heavy political pressure and, as a result, was reluctant to allow the 16-inch gun.