Royal Caribbean will suspend operations globally as of midnight Saturday amid the coronavirus pandemic.

"We will conclude all current sailings as scheduled and assist our guests with their safe return home," according to a statement on the cruise line's website. "As with our announcement yesterday regarding U.S. sailings, we expect to return to service on April 11, 2020."

Major cruise lines including Carnival, Royal Caribbean, Norwegian, and Celebrity announced they would suspend sailing operations to and from U.S. ports for 30 days due to the COVID-19 pandemic, Cruise Lines International Association announced Friday.

Viking and Disney cruises announced similar measures Thursday, before the major cruise association.

“CLIA cruise line members are voluntarily and temporarily suspending operations from the U.S. as we work to address this public health crisis,” said Kelly Craighead, CLIA president and CEO in a statement. “This is an unprecedented situation."

Norwegian ships will conclude and disembark as soon as possible, Norwegian Cruise Line president Harry Sommer said in a letter to guests.

Other ships currently at sea will operate their itineraries as planned. Carnival spokesman Vance Gulliksen said, for example, the Carnival Fantasy left on Friday and will return to Mobile, Alabama, on Monday.

Celebrity Cruise ships that left U.S. ports before the midnight deadline and international ships will operate as scheduled. U.S. ships currently at sea will continue on schedule.

Craighead said that the association was working with the national Centers for Disease Control during the ongoing medical crisis which has severely affected the cruise industry. "This has been a challenging time, but we hope that this decision will enable us to focus on the future and a return to normal as soon as possible."

The suspension will take effect at midnight Friday. CLIA said it will focused on the "safe and smooth return" of those currently at sea on ships.

President Trump tweeted Friday that the cruise suspension came "at my request."

"It is a great and important industry – it will be kept that way!" Trump wrote. Speaking from the White House Rose Garden Friday after declaring a national emergency due to the highly contagious virus, Trump had praise for the "great" cruise industry.

Sommer said in a letter posted on Twitter that there were no confirmed cases across their 17-ship fleet but the company was "taking this measure in abundance of caution, we felt it necessary to do our part."

Sommer made clear passengers affected would receive future credit or refund offers.

In an open letter to passengers posted on its website, Celebrity Cruises said that all booked passengers will get a 125% future cruise credit, which they can use until Dec. 31.

"Should you prefer a 100% refund to your original method of payment you may contact us anytime up until the expiration date," the letter added.

Also Friday, Canada's transport minister, Marc Garneau, said all Canadian ports would be closed to cruise ships carrying more than 500 passengers from April 2 to July 1.

At least 30 cruise ships at sea list port destinations in the USA this week, according to a USA TODAY satellite tracking analysis of 380 of the world’s largest cruise ships. Data from real-time vessel monitoring systems was merged with passenger and crew capacities to produce the snapshot.

That means upward of 100,000 people – 70% of them passengers – could look to come ashore at a range of U.S. ports.

Coronavirus concerns have prompted other cruise lines to suspend their operations.

Princess Cruises, a division of Carnival, said Thursday it won't sail for 60 days. Two of its ships, the Diamond Princess and Grand Princess, have experienced outbreaks of the coronavirus in recent weeks.

More than 700 people aboard the Diamond Princess tested positive, and six of them died. At least two passengers and 19 crew members aboard the Grand Princess also tested positive. The Grand Princess has been disembarking this week in Oakland, California.

Viking Cruises said Thursday it would cease sailing through May 1. Disney Cruises said Thursday it would cancel new departures starting Saturday through the end of March.

On Friday, British cruise Line Cunard said it would pause all North American departures for one month through April 11. Cunard operates cruise ships Queen Mary 2, Queen Victoria and Queen Elizabeth.

The U.S. State Department and the Centers for Disease Control and Prevention have advised Americans, especially those with underlying health conditions, to avoid cruise travel because of the coronavirus.

On Wednesday, Norwegian Cruise Lines began requiring passengers over the age of 70 to submit a medical fitness certificate before boarding.

Former Food and Drug Administration chief Scott Gottlieb told USA TODAY on Monday that no one should be taking a cruise right now.

"This is a very sticky pathogen," he said. "It's an awful risk to pack a lot of people on a cruise ship."

Contributing: Curtis Tate, Morgan Hines, David Oliver, Nick Penzenstadler and Marco della Cava, USA TODAY