MIAMI (Reuters) – Hurricane Igor strengthened rapidly over the Atlantic Ocean on Sunday, becoming a large and dangerous Category 4 storm as it spun menacingly westward.

Igor, capable of causing catastrophic damage, posed no imminent threat to land or energy interests.

But the U.S. National Hurricane Center said Igor was packing top sustained winds of 140 miles per hour, making it a "major" Category 4 storm on the five-step Saffir-Simpson scale of hurricane intensity.

"Igor continues to intensify at a rapid pace," the Miami-based hurricane center said.

It said the storm was located about 1,065 miles east of the Caribbean's northern Leeward Islands at 5 p.m. EDT (2100 GMT).

Some additional strengthening of Igor was expected over the next three days but it was expected to fall short of becoming a Category 5 storm before it begins to weaken gradually on Thursday.

Computer models project Igor, which became the fourth hurricane of the 2010 Atlantic season late on Saturday, would stay in the Atlantic for the coming days and not enter the Gulf of Mexico, where U.S. oil and gas operations are clustered.

Veteran forecaster Jeff Masters said on Sunday on his Weather Underground blog (www.wunderground.com) that Igor may threaten Bermuda but had only a small chance of making landfall on the U.S. East Coast or in Canada.

Masters and other forecasters said it was still too early to make any definitive predictions about Igor's long-term fate, however.

Behind Igor, the hurricane center said a tropical depression off the southernmost Cape Verde islands was just below cyclone strength and poised to become Tropical Storm Julia at any time.

Julia was expected to become a Category 1 hurricane.

The hurricane center was also monitoring a low pressure system over the east-central Caribbean that it said could develop into a tropical cyclone over the next couple of days.

The 2010 Atlantic hurricane season was predicted to be extremely active by most forecasters. Besides Igor, three hurricanes -- Alex, Danielle and Earl -- formed earlier in the season, the last two reaching Category 4 strength.

Several forecasters have said they expect the season to produce in all some five major hurricanes of Category 3 strength or stronger.