Updated

A top U.N. official says the admission of Palestine to the United Nations as a non-member Observer State in 2012 was a historic milestone.

Deputy Secretary-General Jan Eliasson, reflecting on the state of the Israel-Palestinian conflict as part of the U.N.'s "International Day of Solidarity with the Palestinian People," acknowledged both the achievements and lost opportunities related to the conflict as he and Secretary-General Ban Ki-moon near the end of their tenure this year.

Eliasson says the last 10 years can be described as "a lost decade" for Israeli-Palestinian peace-making and if the trend continues, a two-state solution could slip out of reach.

His comments came as the 193-member General Assembly prepared to meet Tuesday afternoon on the conflict.