"Annexing land not part of your country is an act of war. Any Israeli attempt to annex occupied territories will be an offensive act of war." Declaring a country on land that is not yours is an act of war. Any Palestinian attempt to "annex" land by declaring statehood upon it will be an offensive act of war.
4 UN peacekeepers injured in Sinai and taken to hospital in south Israel (Haaretz)
from the article: Palestinians under world pressure not to declare state unilaterally