WASHINGTON (AFP) - Americans by the droves plunked down their cash on Saturday for a chance at fulfilling a feverish dream: winning an estimated US$600 million (S$755 million) Powerball lottery jackpot.

The winning numbers - 10, 13, 14, 22, 52 and a Powerball of 11 - were drawn just before 11pm eastern time (11am Singapore Time Sunday) but contest organisers did not immediately declare if there had been a winner.

If there is no winner, the jackpot could rise to close to US$1 billion by the next scheduled draw on Wednesday.

The US$2 tickets are sold at supermarkets, corner stores and gas stations.

The jackpot is "the largest in the 21-year history of the game," the Iowa state lottery agency said in a statement.

"Strong sales across the country are the reason the prize is taking big jumps now," the organisers said before the draw - particularly after the May 15 draw, when the jackpot stood at US$363.9 million, and there was no winner.

Sales were also boosted after Powerball tickets became available in California starting in April. The game presents a choice of five numbers from a pool of 59, plus a Powerball number from a separate pool of 35.

Powerball - a shared jackpot coordinated by the Multi-State Lottery Association (MUSL), formed by the participating state lotteries - cannot be played from outside the United States or outside participating states.

The richest US jackpot of all time was US$656 million, won in a Mega Millions draw in March 2012 and split between three tickets in Illinois, Kansas and Maryland. Like all US lotteries, the winnings are subject to tax.

Back then, when entering cost US$1, big lines of customers formed for three days, said Rajendra Prasad Bhusal, an employee at the Continental Wine and Liquor store in downtown Washington.

In recent days, hopefuls have again streamed in to buy Powerball tickets, but the crowd is only a third of the numbers seen in March last year, according to the liquor salesman.

"Now, people complain that the tickets cost too much," he added.

The Powerball website says the odds of winning are one in 175,223,510. For a comparison, the chance of getting struck by lighting in the United States is one in 280,000, according to the National Lightning Safety Institute.

The main Powerball website advised that "swinging a live chicken above your head while wishing for the future numbers does NOT work" to improve the chances of winning.

Buying more tickets helps, "but the odds are still high and hitting the jackpot is still a question of fate," it added.