In 2004, The Unites States of America made a promise to Israel that it would not be forced back to the pre-1967 lines (which are the armistice lines of 1949).
In a letter dated April 14, 2004, in connection with the then-planned complete Israeli withdrawal from the Gaza strip, the President of the United States affirmed to the Prime Minister of Israel that "…it is unrealistic to expect that the outcome of final status negotiations will be a full and complete return to the armistice lines of 1949…"
This promise has now been broken by Barack Obama.
In his speech on May 19, 2011, Mr. Obama declared: "The borders of Israel and Palestine should be based on the 1967 lines with mutually agreed swaps…"
These are the "1967 lines" Obama is referring too: