The head of the International Energy Agency warned Monday that the Russian invasion shouldn’t be an excuse for large-scale fossil-fuel investments.

“I do worry about that,” said Fatih Birol, executive director of the IEA, at a World Economic Forum event in Davos, Switzerland. “It will forever close door to reach goal to reach climate targets.”

“But number two, it may not be, as it seems now, a lucrative business,” he said. Everyone talks about clean energy transition. “If they do what they say, even if they do 50% of what they say, those fossil fuel investments may be idle in the future.”

Birol’s comments come as major investors, including Berkshire Hathaway’s BRK.B, -0.03% Warren Buffett, increase their investments in traditional oil and gas companies.

Birol made a wide-ranging plea for companies to boost their energy output, from oil producers with spare capacity at existing fields, but also for shale oil and gas and countries with nuclear capacity such as Belgium. He said countries like Germany building liquefied natural gas plants should spend extra so that they’re ready for amonia or hydrogen as inputs.

German Vice Chancellor Robert Habeck urged countries not to fall prey to protectionism. “We have to stick to global markets,” he said. “If we are only caring for our own food supply and energy supply, it must have disastrous effect on the prices.”

Crude-oil prices CL.1, +1.12% have surged 48% this year, recently exchanging hands at $111.53 per barrel.

See also: Zelenskyy urges ‘maximum’ sanctions on Russia in Davos talk