JERUSALEM -- In eight years on the job, Palestinian President Mahmoud Abbas has seen his share of ups and downs. Thursday's appearance with visiting U.S. President Barack Obama looked like it was one of his lowest points.

At a joint news conference, Obama delivered a stinging rejection to Abbas' key demand that Israel stop building settlements before peace talks resume.

Abbas has long argued that he cannot be expected to negotiate the borders between Israel and a future Palestine while Israel unilaterally determines that line by accelerating settlement construction in the occupied West Bank and east Jerusalem.

The Palestinians had desperately hoped that Obama, an outspoken critic of settlements, would press Israel to halt the construction. Instead, Obama said disagreements should not be used as an "excuse" not to talk.

As the animated Obama explained his positions, the subdued Abbas looked on with a blank expression. When it was his turn to speak, Abbas held his ground, publicly disagreeing with his visitor. An aide later acknowledged Abbas was disappointed.

Abbas now faces two unappealing choices: Cave in and see his tattered credibility suffer further, or stick to his guns while peace efforts stay frozen - and Israel continues to build on the land the Palestinians want for their state.