U.S. oil-supply growth is being hindered by “rapidly escalating” equipment costs and supply-chain snags, ConocoPhillips Chief Executive Officer Ryan Lance said.

The “extremely tight” market for oilfield workers, particularly in the Permian Basin of West Texas and New Mexico, also is squeezing the energy industry and frustrating efforts to expand oil production, Lance said during a conference call with analysts on November 3.

Lance, one of the longest-serving major U.S. oil-company CEOs, also cautioned the federal government against any significant changes to the tax structure. Tweaking the tax code could have dire long-term consequences for oil and natural gas investments, he added.

His comments come just days after U.S. President Joe Biden suggested taxing the oil industry’s so-called windfall profits, which the president called “war profiteering.” Lance said calls for windfall taxes are “not a helpful conversation right now.”