Seven years of relentless conflict in Syria have wreaked destruction that the United Nations said Wednesday has cost the country close to US$400 billion.

The figure was released after a two-day meeting of more than 50 Syrian and international experts in neighboring Lebanon, hosted by the UN's Economic and Social Commission for Western Asia (ESCWA).

ESCWA said the "volume of destruction in physical capital and its sectoral distribution" had been estimated at more than US$388 billion.

More than half of Syria's pre-war population has fled the country or been displaced internally over the past seven years.

ESCWA said a full report on the impact of the war was due out in September and that the updated estimates reached this week would help inform ongoing discussions on post-conflict Syria.

On the same day, Jordan warned that a severe financial shortfall facing a United Nations agency that helps Palestinian refugees could have a "catastrophic" impact on the lives of millions of refugees in the region.

Foreign Minister Ayman Safadi said after meeting visiting U.N. Relief and Works Agency (UNRWA) Commissioner-General Pierre Krähenbühl the budget crisis facing the agency could deprive refugees of core education, healthcare and food security service that would only "deepen their humanitarian plight."

UNRWA has faced a cash crisis since the United States, long its biggest donor, slashed funding to the agency, providing just $60 million of a promised $365 million this year.

U.S. President Donald Trump withheld the aid after questioning its value and saying Washington would only provide more assistance if the Palestinians agreed to renew peace talks with Israel.

Jordan, which hosts the largest number of Palestinian refugees in the Middle East outside Palestinian territories, was engaged in intensive lobbying with donors.