CIA Director William Burns said Tuesday that Ukraine faces a test of staying power against Russia and that if the U.S. cut off support for Kyiv it would be a mistake of “historic proportions.”

In a commentary published in Foreign Affairs, Burns wrote that Russian President Vladimir Putin is betting that time is on his side, “that he can grind down Ukraine and wear down its Western supporters.”

But Burns argued that “the key to success lies in preserving Western aid for Ukraine.”

Adding up to less than 5% of the U.S. defense budget, the aid to Ukraine represents “a relatively modest investment with significant geopolitical returns for the United States and notable returns for American industry,” Burns wrote.

Keeping up arms deliveries to Ukraine would give the government in Kyiv a stronger hand for any possible peace talks and bolster the prospects of Ukraine’s winning in the long term while inflicting a strategic loss for Russia, Burns said. 

“For the United States to walk away from the conflict at this crucial moment and cut off support to Ukraine would be an own goal of historic proportions,” he wrote.

Whether the U.S. continues to assist Ukraine or abandons it will send a clear message to China, he said.

“No one is watching U.S. support for Ukraine more closely than Chinese leaders,” Burns wrote.

Addressing the war between Israel and Hamas, Burns, a former career diplomat, said the Middle East was in a volatile, “explosive” condition.

“I have spent much of the last four decades working in and on the Middle East, and I have rarely seen it more tangled or explosive,” he wrote.

But he said that it was vital to pursue a “durable peace” that would establish a Palestinian state, ensure Israel’s security and normalize relations between Israel and Saudi Arabia and other Arab countries.

Burns also said the key to security for Israel and the region is “dealing with Iran,” though he did not elaborate.

“The Iranian regime has been emboldened by the crisis and seems ready to fight to its last regional proxy, all while expanding its nuclear program and enabling Russian aggression,” he wrote.