Matthew weakened slightly to a Category 4 major hurricane early Saturday as it barreled through the Caribbean, on target to approach Jamaica late Sunday and potentially impact the U.S. East Coast next week.

En route, it also threatens Haiti, Cuba and the Bahamas into Monday.

As of 8 a.m ET, Matthew had maximum-sustained winds of 155 mph — just 2 mph shy of Category 5 status that it reached on Friday. It was moving to the west at 7 mph and was located about 400 miles southeast of Kingston, Jamaica.

The National Hurricane Center said Matthew was expected to turn toward the west-northwest later Saturday followed by a turn toward the north-northwest on Sunday.

A hurricane watch has been posted for Jamaica and a tropical storm watch has been issued for portions of Haiti.

AccuWeather Senior Meteorologist Bernie Rayno said if Matthew moves swiftly as it heads north, it has a greater chance of causing significant impact from rain, wind and flooding along much of the Atlantic coast.

"On the other hand, if Matthew's forward speed slows, it could still have significant impact on the Atlantic coast, but in a much smaller area, when compared to a fast-moving hurricane," he said.

The hurricane center's five-day forecast cone — which marks the range of the storm's possible path — includes a portion of southeast Florida early Wednesday.

The hurricane center also warns of likely life-threatening surf and rip current conditions over a wide area from Puerto Rico to Venezuela.

Sometime on Saturday or early Sunday, Matthew should make its long-anticipated northwest or northward turn in the Caribbean Sea, reported.

In Jamaica, Prime Minister Andrew Holness said government services have been placed on high alert, according to the Jamaica Observer newspaper. Thursday, fishermen on Jamaica’s cays and banks were advised to evacuate immediately and return to the mainland.

Other small craft operators in the island’s coastal waters were also told to return to port, while those in port were advised not to venture out, the newspaper reported.

Florida Gov. Rick Scott said the state emergency operations centers were active on Friday. He said state officials will continue monitoring Matthew's path and urged residents and tourists to monitor the storm and have their emergency plan in place.

"While the National Hurricane Center's current forecast predicts Matthew traveling east of Florida, we all know that the track of these storms can quickly change," Scott said.

A hurricane is classified as "major" when its sustained winds reach 111 mph. A major hurricane is a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale. It's the first major hurricane in September in the Caribbean since Felix in 2007.

Hurricane Matthew is the 5th hurricane and 2nd major hurricane of the 2016 Atlantic hurricane season. It's now the only hurricane or typhoon on the planet.