Artificial intelligence (AI) has made history by beating humans in poker for the first time, the last remaining game in which humans had managed to maintain the upper hand.

Libratus, an AI built by Carnegie Mellon University racked up over $US1.7 million worth of chips against four of the top professional poker players in the world in a 20-day marathon poker tournament that ended on Tuesday in Philadelphia.

In the last two decades computers have bested humans in chess, checkers and the ancient game of Go but poker, which relies on figuring out human behaviour, was previously considered immune to machines.

"The best AI's ability to do strategic reasoning with imperfect information has now surpassed that of the best humans," Liberatus' co-creator professor Tuomas Sandholm said on Wednesday.

Key to Libratus' victory was the machine's ability to outbluff humans.

"The computer can't win at poker if it can't bluff," head of the Computer Science Department at CMU Frank Pfenning said.

"Developing an AI that can do that successfully is a tremendous step forward scientifically and has numerous applications. Imagine that your smartphone will some day be able to negotiate the best price on a new car for you. That's just the beginning."

The win prompted inquiries from companies all over the world seeking to use Libratus' algorithm for problem solving.

"It can be used in any situation where information is incomplete including business negotiation, military strategy, cyber security and medical treatment," Sandholm said.

Dong Kim, one of the four top poker players who participated in the tournament echoed the statement.

"It was about half way through the challenge (with Libratus when) I knew we wouldn't come back," said Kim.

In the 2017 heads-up, no limit Texas Hold'em battle, the four human players only won five days out of 20 and split a $US200,000 prize based on their performance.