Travel warning the State Department advising Americans not to get on a cruise ship.

It comes as that ship held off the coast of California for days is finally being allowed to dock.

But when the Grand Princess arrives tomorrow, most of the 2400 passengers on board will head to federal facilities to be quarantined.

Here's NBC's chief national correspondent, Matt Gutman in San Francisco tonight.

The stunning warning from the U S State Department telling citizens not to travel on cruise ships, especially people with underlying health conditions.

That colossal logistical effort underway.

Government authorities preparing to offload over 2400 passengers board the Grand Princess Cruise ship captain, making the announcement we will arrive at sometime on Monday.

Passengers will be taken to this port in Oakland, the most ill moved off first and sent to hospitals all others taken to military bases in California and Georgia for a mandatory 14 day quarantine.

International passengers will be repatriated to their home countries over the past couple of days.

President Trump has said that he would prefer if none of the passengers aboard these cruises landed on U.

S soil.

Did he mention any of that to you.

Your commerce.

We had a We had a private conversation.

But he said, We're gonna do the right thing and you have my support, all of our support, logistically and otherwise.

So, before he made those statements publicly at a private conversation with them, members of the president's task force admit the plan for tomorrow is still in the works.

The plan will be in place by that time, but I don't I don't want to a preview the plan right now.

Shouldn't you be able to do that?

I think I think it needs to all come from a solitary source.

We shouldn't have 16 people saying what the plan is.

Okay, it has a particularly when it hasn't been fully formulated.

Among those on board at least 1000 of the most vulnerable age group people over 70 the cruise line telling ABC News 500 prescriptions delivered from this supply boat for those in dire need.

All this after tests were choppered aboard the Grand Princess Thursday 21 testing positive anger and frustration boiling over during the past 24 hours.

I kind of feel like we're floating around the drain just waiting here to get the virus.

We haven't been tested.

We want to be tested properly.

And, ah, we want to make sure that we're safe.

ABC News has learned to cruise ships off the coast of Florida were being held on a no sale order.

Crew members who worked on the affected chips being tested more than two weeks after possible exposure on the Grand Princess.

The cruise line says they show no symptoms, and one of the ships has been released to land tonight.

Government officials, with a stark warning to the most vulnerable Americans.

Right now.

Not wait until things get worse.

Say no launch crowds, no long trips and, above all, don't get on a cruise ship.

All right, Mac up Man joins us now live from San Francisco and Matt officials just briefing about the offloading of those passengers.

We imagine there are a lot of people that want to get off that boat, but officials telling you it could take 2 to 3 days, and that's because of the unprecedented logistical scale of this effort.

It begins right now, with the team preparing to board that ship to do triage on passengers.

It continues with taking over part of this port that's able to accommodate that 1000 foot long ship and, of course, continues in just a matter of hours, with the beginning of standing up, what will be likely one of the largest isolation and quarantine facilities in America?

Matt Gutman with those new developments tonight, Matt Thank you.

Hi, everyone.

George Stephanopoulos here.

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