Abbas wants the US to pledge the impossible
Both Obama & Abbas know that Bibi cannot survive if he stops building in Jerusalem and its only because he is building in Jerusalem his coalition partners have accepted a freeze in Judea & Samaria.
Obama also knows that alot of Democrat supporting jews do not want any compromises on Jerusalem and with midterms in November the Democrats can`t afford to upset them to much.
If Abbas had any sense he would stop playing hard to get because Obama is the best friend the palestiians have ever had & the Democrats control Congress which makes it easier for the pro arab anti Israel Democrat president.
Democrats can`t afford to be to anti Israel because of the mideterms & the closer we get to them the less pressure will be put on Israel.
After that Abbas probably has about 6 months before Obama goes into lame duck stage because he is coming into the 2012 presidential election
The he has to start thinking about groups like AIPAC & jewish voters which means he has to be more pro Israel.