Germany's vice chancellor is urging the international community to increase aid to Mideast countries hosting millions of Syrian refugees, saying this is key to slowing migration to Europe.

Sigmar Gabriel says wealthy Gulf states "aren't paying" and suggested the U.S. could contribute more. He spoke ahead of a visit to Jordan that starts Monday.

More than 4 million Syrians have fled civil war in their homeland since 2011, and most live in Jordan, Lebanon, Turkey and Iraq. Growing numbers have left these countries for Europe or returned to Syria in recent months because of cuts in food and cash aid.

Aid agencies requested $7.4 billion for the Syria crisis for 2015, but received only 38 percent.

Gabriel told German TV on Sunday the situation in host countries is "dramatically bad."