McDonald's announced Tuesday it is temporarily closing all of its 850 restaurants in Russia in response to the country's invasion of Ukraine.

The burger giant said it will continue paying its 62,000 employees in Russia "who have poured their heart and soul into our McDonald's brand."

But in an open letter to employees and franchisees, McDonald's President and CEO Chris Kempckinski said closing those stores for now is the right thing to do: "Our values mean we cannot ignore the needless human suffering unfolding in Ukraine."

Kempczinski said it's impossible to know when the company will be able to reopen its stores.

McDonald's has also temporarily closed 100 restaurants in Ukraine and continues to pay those employees.

Kempckinski noted that the Ronald McDonald House Charities in Russia "will continue its full operations, just as RMHC Ukraine is partnering with local hospitals and providing humanitarian aid throughout the country."

"The Ronald McDonald House Charities (RMHC) Poland Care Mobile is at the Polish-Ukrainian border to provide medical care and humanitarian aid for families and children, and another Care Mobile is on the way from RMHC Latvia," he said. "Additionally, RMHC Ukraine is deploying medical supplies and providing humanitarian aid throughout the country, and its programs are being repurposed for use by hospital personnel."

McDonald's could take a big financial hit because of the closures. In a recent regulatory filing, the Chicago-based company said its restaurants in Russia and Ukraine contributed 9% of its annual revenue, or around $2 billion.

"The situation is extraordinarily challenging for a global brand like ours, and there are many considerations," Kempczinski said. "For 66 years, we have operated with the belief that communities are made better when there’s a McDonald’s nearby."

Unlike other big fast food brands in Russia that are owned by franchisees — including KFC, Pizza Hut and Burger King — McDonald's owns 84% of its Russian locations.

Pressure has been mounting for McDonald's and other companies such as Coca-Cola and PepsiCo that remain in Russia to pull out. Many corporations have ceased operations in the country in protest of the Ukraine invasion.