In a December 1969 speech, US Secretary of State William P. Rogers said that "any changes in the pre-existing armistice lines should not reflect the weight of conquest and should be confined to insubstantial alterations required for mutual security. We do not support expansionism." Harvard law professor Stephen M. Schwebel responded that "...modifications of the 1949 armistice lines among those States within former Palestinian territory are lawful (if not necessarily desirable), whether those modifications are...'insubstantial alterations required for mutual security' or more substantial alterations—such as recognition of Israeli sovereignty over the whole of Jerusalem." In a footnote, he wrote: "It should be added that the armistice agreements of 1949 expressly preserved the territorial claims of all parties and did not purport to establish definitive boundaries between them."