Unified heavyweight world titleholder Anthony Joshua's mandatory defense against Kubrat Pulev, scheduled for Oct. 28 at Principality Stadium in Cardiff, Wales, will be televised live on Showtime in the United States, the network announced Thursday.

However, to keep Joshua on Showtime for his fourth title defense and fifth consecutive bout, the network had to match an aggressive bid by rival network HBO, according to a source with knowledge of the deal.

Joshua's initial three-fight contract with Showtime had expired, allowing Matchroom Boxing promoter Eddie Hearn to talk to other networks about a deal. But Showtime retained the right of first negotiation and a matching right if any other network beat its offer.

HBO had plans for fall fights involving junior welterweight world champion Terence Crawford and junior lightweight titlist Vasyl Lomachenko, but when the fighters left the network as part of promoter Top Rank's long-term deal with ESPN, it left HBO with money to spend. HBO bid $1.6 million on Joshua-Pulev, far more than Showtime's original offer. Hearn was obligated to take HBO's offer back to Showtime, which matched HBO's bid and landed the fight.

The fight gives Showtime two consecutive weeks of major heavyweight action. A week after Joshua defends against Pulev, world titleholder Deontay Wilder (38-0, 37 KOs) will make his sixth title defense when he faces top contender Luis "King Kong" Ortiz (27-0, 23 KOs) on Nov. 4 at Barclays Center in Brooklyn, New York. Those four heavyweights are among the top five heavyweights in the ESPN.com divisional rankings.

"There's so much to be excited about in the sport of boxing, and it all comes to a fever pitch on consecutive Saturdays this fall on Showtime," said Stephen Espinoza, executive vice president and general manager of Showtime Sports. "This has been a great year for boxing. More specifically, it has been a great year for Showtime boxing. There's no better way to end it than with two major heavyweight world championship events. We are proud to be in business with the two biggest punchers in the sport, Anthony Joshua and Deontay Wilder, and the rest of the talented and hungry heavyweight challengers of today."

England's Joshua (19-0, 19 KOs), 27, will be fighting for the first time since stopping former longtime world champion Wladimir Klitschko in the 11th round before 90,000 at Wembley Stadium in London on April 29 in an epic battle that is the leading fight of the year candidate. A crowd of around 80,000 is expected in Cardiff for the fight with Pulev.

Pulev (25-1, 13 KOs), 36, of Bulgaria, suffered his only defeat when Klitschko scored a crushing fifth-round knockout against him in a November 2014 world championship fight in what was that year's knockout of the year. Pulev, who will be fighting in the United Kingdom for the first time, has won five fights in a row since, including a decision against British contender Dereck Chisora and a third-round destruction of faded former world titleholder Samuel Peter.