President Donald Trump tweeted Friday that four major cruise ship companies have agreed to suspend trips from the U.S. for 30 days, effective at midnight.

Trump said Carnival, Royal Caribbean, Norwegian and MSC Cruises agreed to the suspensions. He said the cruise line industry is a “great and important industry – it will be kept that way!”

The U.S. State Department advised Sunday against any travel on cruise ships, particularly for those with underlying health conditions. The advisory said the CDC has noted an “increased risk of infection of COVID-19 in a cruise ship environment.”

Cruise industry leaders met last weekend with Florida Gov. Ron DeSantis and Vice President Mike Pence and were asked to devise and fund ways to transport any passengers found to carry the virus. Cruise line heads agreed to enhance entry and exit screenings and establish shipboard testing, along with new quarantine standards. Some of the new protocols were expected to start taking effect early this week.

Before the president’s tweet, three cruise lines reported they were suspending operations due to the coronavirus pandemic.

Royal Caribbean, Norwegian and Costa Cruises said they are temporarily halting operations, according to reports.

Royal Caribbean announced a voluntary suspension, according to reporter Walter Bloomberg.

Norwegian Cruise Line Holdings announced a voluntary suspension for its three cruise brands. Norwegian's brands include Norwegian Cruise Line, Oceania Cruises and Regent Seven Seas Cruises.

Italy-based Costa Cruises will suspend all operations through April 3 due to the coronavirus pandemic, the company’s president announced Friday.

The move by Carnival Corporation’s Italian fleet came a day after two other major global cruise lines announced a temporary halt to their operations.

Neil Palomba said the company has been closely following the advice of health officials aboard all its 14 ships. He said, however, that new government restrictions required its vessels to port until the global crisis is over.

He said this was the first time in the company’s 70-year history that such a measure had to be taken.

The latest suspension of cruises comes a day after Princess Cruises and Viking Cruises announced plans to temporarily shutter operations until at least April 30.

Princess Cruises operates three of the vessels that have been recently stricken by the virus:

The Diamond Princess, which was quarantined Feb. 4 with 3,700 passengers off the coast of Japan with more than 700 infected; and the Grand Princess, which had been quarantined off the coast of San Francisco with 3,500 aboard and 21 confirmed with the virus.

A third Princess Cruises ship, The Caribbean Princess, was also being isolated in Fort Lauderdale, Florida, while crew members get tested for the virus.

The Diamond and the Grand have since been evacuated and passengers taken to military bases around the country, including Dobbins in Marietta, Georgia, where they are being quarantined.

Costa Cruises is based in Genoa, Italy.

The Associated Press contributed to this report.