LONDON - OPEC's chief on Tuesday cautioned crude-producing countries against cutting spending on projects to boost their capacity in response to an International Energy Agency report predicting the United States will not need to import oil in the future.

Abdalla Salem el-Badri, secretary general of the Organization of the Petroleum Exporting Countries, said reining in such investment would be disastrous for the world because the U.S. won't remain self-sufficient long.

If countries don't invest in efforts to produce more hydrocarbons, "there will be a shortage [of oil]. The price will be very high," he said in an interview.

"We want other [non-U.S.] producers to invest."

On Monday, the IEA predicted the U.S. will overtake Saudi Arabia as the world's largest oil producer by 2020 thanks to a shale output boom.

El-Badri said the U.S. can be self-sufficient and export for a short while. "Then they will have to go back as importers," he said. "This is not sustainable in the long term."

While urging oil-producing nations not to cut back on investment, he said this should not be construed as hostility to U.S. oil production.

"We have nothing against them," he said. He described shale oil as "a new addition, a great discovery," adding "there is room for any kind of energy."

The 12 OPEC countries produce more than a third of the oil consumed by the world every day.