The launch initially scheduled for Sunday was pushed back a day due to "unfavourable" sea conditions, Blue Origin posted on X.

Named New Glenn after a legendary astronaut, the rocket stands 320 feet (98 meters) tall, roughly equivalent to a 32-story building -- and is set to blast off from Cape Canaveral Space Force Station in a launch window that now opens at 1:00 am (0600 GMT) Monday.

"Pointy end up!" the company's CEO, Dave Limp posted on X alongside photos of the gleaming white behemoth.

With the mission dubbed NG-1, Bezos, the world's second-richest man, is taking direct aim at the world's wealthiest: Elon Musk, whose company SpaceX dominates the orbital launch market through its Falcon 9 and Falcon Heavy rockets.

These serve the commercial sector, the Pentagon, and US space agency NASA -- including, crucially, ferrying astronauts to and from the International Space Station.

"SpaceX has for the past several years been pretty much the only game in town, and so having a competitor... this is great," G. Scott Hubbard, a retired senior NASA official, told AFP.

SpaceX, meanwhile, is planning the next orbital test of Starship -- its gargantuan new-generation rocket -- the very next day, upping the sense of high-stakes rivalry.

- Landing attempt -

If all goes to plan, shortly after launch, Blue Origin will attempt to land the first-stage booster on a drone ship named Jacklyn, in honor of Bezos's mother, stationed about 620 miles (1,000 kilometers) downrange in the Atlantic Ocean.

Though SpaceX has long made such landings a near-routine spectacle, this will be Blue Origin's first shot at a touchdown on the high seas.

Meanwhile, the rocket's upper stage will fire its engines toward Earth orbit, carrying a Defense Department-funded prototype spaceship called Blue Ring, which will remain aboard for the roughly six-hour test flight.

Limp emphasized that simply reaching orbit is the prime goal, while successfully recovering the booster would be a welcome "bonus."

Blue Origin has experience landing its New Shepard rockets -- used for suborbital tourism -- but they are much smaller and land on terra firma rather than a ship at sea.

Physically, New Glenn dwarfs the 230-foot Falcon 9 and is designed for heavier payloads.

It slots between Falcon 9 and its big sibling, Falcon Heavy, in terms of mass capacity but holds an edge with its wider payload fairing, ideal for transporting more voluminous cargo.

- Slow v fast development -

Blue Origin has already secured a NASA contract to launch two Mars probes aboard New Glenn. The rocket will also support the deployment of Project Kuiper, a satellite internet constellation designed to compete with Starlink.

For now, however, SpaceX maintains a commanding lead, while other rivals -- United Launch Alliance, Arianespace, and Rocket Lab -- trail far behind.

Like Musk, Bezos has a lifelong passion for space. But whereas Musk dreams of colonizing Mars, Bezos envisions shifting heavy industry off-planet onto floating space platforms in order to preserve Earth, "humanity's blue origin."

He founded Blue Origin in 2000 -- two years before Musk created SpaceX -- but has adopted a more cautious pace, in contrast to his rival's "fail fast, learn fast" philosophy.

"There's been impatience within the space community over Blue Origin's very deliberate approach," Scott Pace, a space policy analyst at George Washington University and former member of the National Space Council, told AFP.

If New Glenn succeeds, Pace added, it will give the US government "dissimilar redundancy" -- valuable backup if one system fails.

Musk's closeness to President-elect Donald Trump has raised concerns about potential conflicts of interest, especially with private astronaut Jared Isaacman -- a business associate of Musk -- slated to become the next NASA chief.

Bezos, however, has been making his own overtures, paying respect to his former foe during a visit to Trump's Mar-a-Lago residence, while Amazon has said it would donate $1 million to the inauguration committee.