RAMALLAH, West Bank — The Palestinian leader, Mahmoud Abbas, on Sunday dismissed a new effort by the Trump administration to encourage investment of more than $50 billion to jump-start the Palestinian and regional economies in hopes of building a foundation for a future peace.

In a rare meeting with foreign journalists at his headquarters in the West Bank city of Ramallah, Mr. Abbas, the Palestinian Authority president, said the plan, set to be kicked off this week at a conference in Bahrain, was ill-begotten and bound to fail.

The Trump administration released its economic plan over the weekend to set the stage for a workshop on Tuesday and Wednesday. The Palestinian leadership called for a boycott of the conference, and Palestinian officials will not attend. Most Palestinian businesspeople who were invited appear to be staying away.

“We need the money and, really, we need assistance,” said Mr. Abbas, who presides over a divided Palestinian polity that has long depended on the largess of donor nations and that is in perpetual financial crisis. “But before everything, there is a political solution.”