Hoping to use economic promise as a bridge to a peace deal between Palestinians and Israel, U.S. Secretary of State John Kerry announced an estimated $4 billion development proposal for the West Bank on Sunday that he said could cut the 21 percent unemployment rate by two-thirds.

"The greatest existential threat and the greatest economic threat to both sides is the lack of peace," Kerry said. "To not try to head these off would be tragic, and it would be irresponsible."

International business leaders rallied by former British Prime Minister Tony Blair will propose new agricultural, construction and other investment to the Palestinian Authority that could increase the Palestinian gross domestic product by 50 percent over three years, Kerry said.