Various issues, including intelligence operations performed by both countries and tensions in Germany and Afghanistan, threatened to forestall the possibility of an agreement between the United States and the Soviet Union. Nonetheless, both Gorbachev and Reagan agreed to continue arms control negotiations at the October 1986 Reykjavík Summit. At the summit, Gorbachev and Reagan closed in on an agreement to greatly reduce or eliminate the nuclear stockpiles of both the U.S. and the Soviet Union over a ten-year period, but the deal collapsed due to disagreements regarding SDI development. Reagan attacked Gorbachev in a 1987 speech delivered in West Berlin, but negotiations continued. Gorbachev and Reagan broke the impasse by agreeing to negotiate separate treaties on intermediate nuclear forces (such as intermediate-range ballistic missiles) and strategic arms (such as intercontinental ballistic missiles).