Carl Icahn seems to be losing his enthusiasm for Occidental Petroleum (OXY -0.09%). The high-profile investor's Icahn Capital divulged in a regulatory filing Monday that it will sell up to 30 million shares of the oil and gas company, which at the maximum would constitute nearly 28% of Icahn's total holding.

In the filing, Icahn Capital said the move was merely a repositioning.

"While we still believe in Occidental, our investment has become somewhat of an outsized position in our investment portfolio, and as a result, we believe it is prudent to reduce the size of our position to rebalance our portfolio," the would-be seller wrote.

Toy oil rig and barrel atop various denominations of currency.

Image source: Getty Images.

At the moment, Icahn Capital and other entities affiliated with the billionaire investor are collectively Occidental's third-largest shareholder; their more than 107.9 million-share holding comprises nearly 12% of the company's shares outstanding tally.

The announcement comes barely one year after Icahn dramatically increased his stake in the company, from an approximate 2.5% to around 10%. At the time, the activist investor was sharply critical of Occidental management for the way it acquired its peer Anadarko Petroleum. The $55 billion deal generated a significant pile of debt for Occidental, a challenging situation that has since been exacerbated by the coronavirus pandemic's damaging effects on the oil industry.

Occidental has not yet officially commented on Icahn Capital's announcement.

This is not ideal timing for Occidental, since like its peers it could use a note of confidence or several from its major shareholders. On Monday the stock closed 4.3% lower, in contrast to the nearly 0.7% gain of the S&P 500 index.