Washington: Donald Trump has accused rival Hillary Clinton of getting pumped up ahead of presidential debates with performance-enhancing drugs and challenged her to take a drug test before the final debate next week, giving the gruelling race to the White House a bizarre new direction.

The 70-year-old outspoken billionaire Republican nominee, who has been trailing the Democrat in national polls, questioned the physical stamina of Clinton, 68, arguing that she was more energetic during the beginning of their debate last Sunday, but lost her steam by the end of the debate. He offered no evidence to back his unsubstatiated claim.

At the beginning of her last debate, she was all pumped up, but at the end she was all 'take me down.' She could barely reach her car, Trump told to loud cheers among his supporters during a rally in New hampshire.

“I think we should take a drug test. Anyway, I'm willing to do it,” Trump said. His personal attacks on Clinton have increased lately, with he previously calling her Crooked Hillary and that he would send her to jail if he was elected president in the election on November 8.

He has described Clinton as not having the stamina to be the president of the United States, after the former secretary of state had a scaring ' health episode' when she stumbled and nearly collapsed during the 9/11 memorial event last month. Clinton was later diagnosed with pneumonia and her health had become a talking point in the electoral race.

His comment yesterday that she could barely reach her car appeared to be aimed at the 9/11 ceremony incident. Referring to the 17 Republican nominees he has trounced in the primaries, Trump, compared himself with an athlete and said every athlete takes a drug test before the competition. We're like athletes, but athletes, they make them take a drug test. We should take a drug test. I think we should take a drug test prior to the debate because I don't know what's going on with her, Trump said.

Trump's accusations against Clinton came as he outlayed his policy to fight the drug abuse in New Hampshire, a state that has become a flashpoint in the battle against the menace.

The third Trump-Clinton presidential debate is scheduled for Wednesday in Las Vegas. Clinton was declared a clear winner in first debate. She won the second too according voters in opinion polls, but Trump was declared as having performed better-than-expected.

Trump has been dwarfed by a barrage of sexual assault allegations, including videos in which he was seen bragging about groping women, and has been virtually abandoned by his own Republican party.

He has been repeatedly cast doubt on the fairness of the US presidential election at election rallies, saying it is being rigged by a corrupt media publishing outright lies. Instead of being held accountable, Hillary is running for President in what looks like a rigged election.

The election is being rigged by corrupt media, pushing completely false allegations and outright lies, in an effort to elect her President, Trump told his supporters at the Hampshire rally.