AMMAN (Reuters) - Syrian opposition chief Ahmad Jarba will tell Western and Arab allies on Tuesday the group will not attend peace talks unless the goal is to remove President Bashar al-Assad from power.

Jarba will say the opposition risks losing credibility if it yields to international pressure to attend talks that do not aim at Assad's removal, according to a text of the speech he will make to a "Friends of Syria" meeting in London, seen by Reuters,

"The people will not believe us and will regard us as traitors to the revolution and to the blood of the rebels," Jarba will say, according to the text.

The United States and Russia said in May they would convene a "Geneva 2" conference to try to end a conflict that has killed well over 100,000 people and forced millions from their homes, but it faces huge obstacles and no firm date has been set.

Western nations and their Middle Eastern allies pressed Jarba's opposition Syrian National Coalition on Tuesday to join the talks, although Assad has made clear he will not step down.

"The Sultan must leave," Jarba said in the speech text, in reference to Assad. "Geneva cannot succeed and we cannot take part if it allows Assad to gain more time to spill the blood of our people while the world looks on."

British Foreign Secretary William Hague, hosting the meeting of 11 nations, said beforehand that it was vital that all elements of the Western-backed Syrian opposition join the talks.

(Reporting by Khaled Yacoub Oweis; Editing by Alistair Lyon)