* Gasoline floating storage seen at over 400,000 tonnes in April
* European exports to West Africa, United States already rising
LONDON, April 6 (Reuters) - Gasoline stored in ships off Europe's coast has ballooned to more than 400,000 tonnes, putting pressure on the continent's traders to compete for buyers once summer demand starts.
Several vessels have joined the three initially booked to store fuel off Europe's ports in mid-March, and brokers said even barges have held cargoes of gasoline for three to four weeks as the volumes traded in Europe hit record levels last month.
The tankers Torm Tevere, Ridgebury John B and STI Clapham are now parked off Europe's Amsterdam-Rotterdam-Antwerp hub, where on-land stocks hit a record 1.387 million tonnes last week, according to figures from PJK International.
Fuel in vessels, rather than in tanks on land, is typically the most expensive way to store fuel, so notable volumes of floating storage only build when the market is oversupplied. Volumes off the coast of Europe have risen from just over 250,000 tonnes in mid-March.
Traders said the atypical floating fuel stores will target hungry buyers in the United States and the Middle East as the former restock following maintenance and the latter stock up before Ramadan. Already, some cargoes that had been parked off Europe's coast, such as the Nan Lin Wan, are sailing for buyers in New York Harbor.
Expectations that prices in the coming months will rise above the current levels also created the market condition, known as contango, that allowed traders to make money storing the fuel in these tankers.
Profits for gasoline have also risen significantly since late last month as the market shifted to summer-quality fuel -- and sellers cleared their backlog of winter grades.
Industry monitor Genscape showed a spike in the amount of gasoline booked to sail from Europe to West Africa and the Americas in the week to March 30, rising to more than 700,000 tonnes for the former and more than 400,000 tonnes for the latter.
But analysts said the owners of the fuel - and refineries in Europe - could run into trouble if demand does not come in particularly strong over the summer.
"We're just dealing with the fact that there is a fair amount (of fuel) out there," said Robert Campbell, head of oil products research with consultancy Energy Aspects. "ARA stocks are full. There's not the same sort of pull from the Middle East, and China is still exporting."
Chinese state energy giant CNPC said it had sold its first ever gasoline to the Americas, an indication of the ample supply in Asia that has also seen top trader Vitol store gasoline on tankers.
Cargo tracking firm Kpler said that there is Korean gasoline on the Marlin Ammolite heading for Ecuador, and Chinese gasoline aboard the BW Wren en route to Mexico, underscoring the coming fight for buyers.
(Additional reporting by Ron Bousso; Editing by Adrian Croft)