BERLIN (Reuters) - The German government has pledged to significantly increase its funding for the U.N. agency that supports Palestinian refugees after the United States cut its aid.

German Foreign Minister Heiko Maas said the funding crisis for the United Nations Relief and Works Agency (UNWRA) was fuelling uncertainty.

“The loss of this organisation could unleash an uncontrollable chain reaction,” he said.

Germany had already provided 81 million euros (72.66 million pounds) in aid for UNWRA this year, he said, and was preparing to increase its contribution. He gave no figure.

“We are currently preparing to provide an additional amount of significant funds,” Maas said in a letter to European Union foreign ministers that was seen by Reuters.

Maas said it was clear that the added German funds would not cover a $217 million deficit left by the U.S. withdrawal, and urged the European Union and other states to work towards “a sustainable finance basis for the organisation”.

It is part of a broader push by Maas to take a more assertive stance in disagreements with the United States on a range of issues including trade, military spending and climate change.

Jordan said on Thursday it would lead a campaign to raise funds to help the U.N. agency survive, including an appeal to the Arab League.

UNRWA has faced a cash crisis since the United States, long its biggest donor, earlier this year slashed funding, saying the agency needed to make unspecified reforms and calling on the Palestinians to renew peace talks with Israel.

The agency was founded in 1949 after the first Arab-Israeli war, in the wake of the exodus of around 700,000 refugees who fled or were driven out of Israel on its founding as a state.

UNRWA now looks after more than 5 million people in Jordan, Lebanon, Syria and the Palestinian territories of the West Bank and Gaza Strip.