The Coast Guard says it cannot guarantee the rescue of the tourist submarine OceanGate Titanic

The US Coast Guard has issued the gloomy warning that it may not be able to rescue the missing Titanic tourist submarine – even if it does find it.

The submarine Titan has been missing since 9:45 a.m. Sunday after launching into the Atlantic Ocean at 8:00 a.m.

OceanGate Expeditions – the company that organizes the tours and is responsible for the submarine – did not notify the Coast Guard until 5:40 p.m.

There are five people on board, including three wealthy tourists, and the submarine’s oxygen supply is now just 40 hours, giving rescue crews until Thursday morning to find it before it runs out.

But even if they locate the missing craft in time, there is no certainty that it can be safely brought to the surface.

At a press conference at the US Coast Guard Station in Boston – which coordinates the search and rescue effort – First District Response Coordinator Capt. Jamie Frederick admitted on Tuesday that rescue was not guaranteed.

Scroll down for video

Speaking at a press conference at the U.S. Coast Guard Station in Boston – which coordinates search and rescue efforts – First District Response Captain Jamie Frederick said it was not certain the submarine could be rescued – even if it is found today.

The company's Titan submarine sank about 400 miles southeast of St. John's, Newfoundland, at 8 a.m. Sunday morning, according to the U.S. Coast Guard.  It lost contact at 9:45 a.m. but was not reported to the Coast Guard until 5:40 p.m.

The company’s Titan submarine sank about 400 miles southeast of St. John’s, Newfoundland, at 8 a.m. Sunday morning, according to the U.S. Coast Guard. It lost contact at 9:45 a.m. but was not reported to the Coast Guard until 5:40 p.m.

“Even with that much time left, if you found the sub right now, would that give you enough time to save those five people on board?” he was asked.

TIMELINE OF MISSING DIP POINT TITAN

8 a.m. Sunday: Titan submerges about 900 miles east of Cape Cod

9:45 am: Expedition ship Polar Prince loses contact with submarine

5:40 pm: Coast Guard first issued warning of missing submarine

9:13 pm: Canadian Coast Guard alerted

Thursday at 8 a.m.: 96 hours of oxygen running out

“I don’t know the answer to that question… all I know is that we will do everything in our power to effect a rescue,” Frederick replied.

The Coast Guard has already searched 7,600 square miles of ocean — a search area the size of Connecticut.

At 12,500 feet underwater, few ships can dive deep enough to find it.

The only ones that can search the ocean floor are remote controlled vehicles that are now searching the ocean.

If they find the sub, getting it to the surface is quite another feat, requiring specialist equipment not yet on site.

Other experts likened it to requiring a 2.5-mile cable to lasso to the far side of the moon.

There are multiple civilian vessels assisting in the search, along with U.S. Navy, Canadian Navy, and aircraft.

Among the equipment now en route to the site is a decompression chamber for the five passengers should they be brought to the surface.

“Getting salvage equipment on site is the top priority,” Frederick said.

Shahzada Dawood, 48, (pictured with his wife Christine), a UK-based board member of the Prince's Trust charity, and his son Sulaiman Dawood, 19, are among the five missing in the submarine that left to rescue the wreck of the Titanic, that was revealed today

19-year-old Sulaiman Dawood, missing aboard the submarine, is pictured with his mother Christine

Shahzada Dawood, 48, (pictured with his wife Christine), a UK-based board member of the Prince’s Trust charity, and his son Sulaiman Dawood, 19, are among the five missing in the submarine that left to rescue the wreck of the Titanic, that was revealed today

One of the participants in the expedition is billionaire Hamish Harding (pictured), CEO of Action Aviation in Dubai.  He excitedly posted on social media that he was there on Sunday

One of the participants in the expedition is billionaire Hamish Harding (pictured), CEO of Action Aviation in Dubai. He excitedly posted on social media that he was there on Sunday

French naval veteran PH Nargeolet is believed to be taking part in the expedition, although it is unclear if he is aboard the missing submarine

OceanGate CEO Stockton Rush would also be on board

French Navy veteran PH Nargeolet (left) is believed to be taking part in the expedition, along with Stockton Rush (right), CEO of the OceanGate expedition

The search site is located about 900 miles off the coast of Cape Cod, 400 miles southeast of Newfoundland.  It's hard enough to get there without finding the missing submarine below the ocean's surface

The search site is located about 900 miles off the coast of Cape Cod, 400 miles southeast of Newfoundland. It’s hard enough to get there without finding the missing submarine below the ocean’s surface

At 09:45 - one hour and 45 minutes into the dive - it lost contact with its mothership, the Polar Prince.  But it was not reported missing to the U.S. Coast Guard until eight hours later at 5:40 p.m.  The Canadian Coast Guard was not notified until later - 9:13 PM on Sunday night.

At 09:45 – one hour and 45 minutes into the dive – it lost contact with its mothership, the Polar Prince. But it was not reported missing to the U.S. Coast Guard until eight hours later at 5:40 p.m. The Canadian Coast Guard was not notified until later – 9:13 PM on Sunday night.

The logistical challenge is enormous; the wreck of the Titanic is about 400 miles southeast of St Johns, Newfoundland – about 900 miles east of Cape Cod.

A Canadian Coast Guard cutter is expected to arrive in the search area tonight.

It takes several days for Coast Guard ships to reach the site from the US.

In addition to the Coast Guard’s remotely operated underwater vehicles and vessels, several aircraft are surveying the water for signs of the submarine on the surface.

“We don’t want to exhaust one possibility instead of the other. We don’t want to rule out that it’s on the surface.

“If it’s on the surface, we’re pretty sure we can find it,” added Coast Guard 1st District Captain Robert Simpson.

DailyMail.com previously revealed that it took OceanGate eight hours to report the submarine missing.

The company has not yet explained why it took so long to raise the alarm.

The 21ft submarine has an oxygen supply of up to 96 hours

The 21ft submarine has an oxygen supply of up to 96 hours