According to Robert W. Tucker, Professor Emeritus of American Foreign Policy at Johns Hopkins University and David C. Hendrickson, a Professor at Colorado College, Zimmermann may have scuttled the Lisbon Agreement also known as Carrington-Cutileiro peace plan. That was an agreement that would have made peace between three main ethnicities, Bosniaks, Serbs, and Croats, living within the bounds of Bosnia and Herzegovina by the creation of a cantons system, such as exist in Switzerland. At a time when Bosnia-Herzegovina was sliding into war along ethnic lines, this plan proposed ethnic power-sharing on all administrative levels and the devolution of central government to local ethnic communities. On 28 March 1992, ten days after the agreement had been signed by each of the three sides, Zimmermann came to Sarajevo to meet with Alija Izetbegović, president of the Presidency of Bosnia and Herzegovina, giving Izetbegović assurances of U.S. support for a full independent nation without internal division.