NEW YORK (AP) — Billionaire investor Carl Icahn is offering Dell shareholders a chance to own a bigger stake in the company in hopes of thwarting an attempt by Dell's founder to buy it and take it private.

Icahn, who owns a nearly 9 percent stake in Dell, is now offering warrants in addition to the cash he previously offered.

Under his revised offer, shareholders could receive $14 per share, plus one warrant for every four of their shares. The warrant would give shareholders the right to buy one Dell share for $20 over the next seven years.

In a letter to shareholders, Icahn values his offer at about $15.50 to $18 per share.

Michael Dell and Silver Lake Partners have offered $13.65 per share for the company.

Dell shares slipped 4 cents to $13.31 in morning trading.