The war in Ukraine has become “a war of attrition,” and Western nations must prepare for “the long haul,” NATO chief Jens Stoltenberg warned on June 2 following talks with U.S. President Joe Biden.

“Wars are by nature unpredictable and therefore we just have to be prepared for the long haul,” Stoltenberg told reporters after meeting Biden at the White House.

While reiterating that NATO does not want to enter direct confrontation with Russia, Stoltenberg said the Western military alliance has a “responsibility” to support Ukraine.

Stoltenberg said Ukrainians are “paying a high price for defending their own country,” but Russia is also “taking high casualties.”

The war most likely will end at the negotiating table, he said, adding that what happens during talks “is very closely linked to the situation on the ground, on the battlefield.”