He can't say it on the record but with Hamas in control of Gaza it suits him just fine this siege. It gets Hamas out of his hair and he has an excuse to condemn Israel which is going to rally support for himself in Judea & Samaria. It suits Israel because it controls what goes in and out of Gaza which weakens Hamas ability to carry out terror and as it makes Abbas happy then Obama likes it as well. Unless Abbas tells him to or if he thinks its going to cost the Democrats seats in November he will do nothing..... if Obama was unhappy about the siege he would have demanded an end to it long ago.
Obama to meet with Jordan's King Abdullah in White House later this month (Reuters)
from the article: U.S. lawmakers to Obama: Press Israel to ease Gaza siege