DOHA (Reuters) – Qatar said on Friday that economic development needed for Israeli-Palestinian peace could not be achieved without “fair political solutions” acceptable to Palestinians, referring to a U.S. plan set to be unveiled next month.

The White House will lay out the first part of President Donald Trump’s long-awaited Israeli-Palestinian peace plan when it holds an international conference in Bahrain in late June.

The plan, touted by Trump as the “deal of the century,” is expected to encourage investment in the West Bank and Gaza Strip by Arab donor countries before grappling with thorny political issues at the heart of the conflict.

Palestinian officials have rebuked the U.S. effort, which they believe will be heavily biased in favour of Israel.

Qatar’s Foreign Ministry, in a statement, commented on the upcoming conference: “Tackling these challenges requires sincerity of intent, concerted efforts from regional and international players and appropriate political conditions for economic prosperity.

“These conditions would not be achieved without fair political solutions to the issues of the peoples of the region, especially the Palestinian issue, in accordance with a framework acceptable to the brotherly Palestinian people,” the statement said.

Qatar, a close U.S ally and home to its largest Middle East air base, has poured millions of dollars into the impoverished Gaza strip over the past year to boost its ailing economy, and this month pledged an additional $480 million to support both Gaza and the West Bank.

The tiny Gulf state has not said whether it will attend the June 25-26 conference in Manama, which is expected to include representatives and business executives from Europe, the Middle East and Asia, including some finance ministers.

Chief among the Palestinians’ concerns is whether the plan will meet their core demand of calling for them to have an independent state in the West Bank, east Jerusalem and the Gaza Strip — territory Israel captured in the 1967 Arab-Israeli war.

Trump’s Middle East team, led by his senior adviser and son-in-law Jared Kushner, has declined to say whether the plan includes a two-state solution, a central goal of other recent peace efforts that is widely endorsed internationally.