After the fall of the Berlin Wall, Kohl affirmed that former German territories east of the Oder-Neisse line were definitively part of Poland, thereby relinquishing any claim Germany had to them in a treaty signed on 14 November 1990 in Warsaw. Though, earlier in March of that year, Kohl caused a diplomatic firestorm when he suggested that a reunified Germany would not accept the Oder–Neisse line, and implied that the Federal Republic might wish to restore the frontier of 1937, by force if necessary. After the statement caused a major international backlash that threatened to halt German reunification, Kohl retracted his comments after knuckling under international rebuke, and assured both the United States and the Soviet Union that a reunified Germany would accept the Oder–Neisse line as the final border between Poland and Germany. In 1993, Kohl confirmed, via treaty with the Czech Republic, that Germany would no longer bring forward territorial claims as to the pre-1945 ethnic German Sudetenland. This treaty was a disappointment for the German Heimatvertriebene ("displaced persons").