Gustav gathered force and slammed into Cuba as a Category 4 hurricane Saturday, giving oil bears and stock market bulls cause for concern.

Forecasters said the hurricane would come close to the highest rating, Category 5, on Sunday as it rolled into the Gulf of Mexico, according to the

AP

. It would likely then weaken slightly before slamming into the U.S. Gulf Coast as early as Monday, the

AP

added.

Oil prices have been a key driver of stock prices this year (with the two asset classes moving inversely to one another), and Gustav's trajectory means

he could cut Gulf Coast production and boost crude prices.

Crude futures settled Friday at $115.46.

More than 240,000 Cubans were being evacuated as Gustav bore down on the country's western end, and millions of Americans were leaving Gulf Coast towns like New Orleans, which was devastated by Hurricane Katrina three years ago, the

AP

reported.

The U.S. National Hurricane Center said Gustav had sustained winds of 150 mph as the storm's center started to hit the Cuban island province of Isla de Juventud, according to the

AP

. Storms with winds above 155 mph are classified as Class 5.

Gustav has already killed 81 people in other Caribbean nations by causing floods and landslides, the

AP

reported.

This article was written by a staff member of TheStreet.com.