Agar, who has been named in Australia's T20 World Cup campaign, will join the squad after the completion of the tournament, and will replace Raza when he heads off on national duty for Zimbabwe in their series against India.

"I'm delighted to be joining the Steelbacks in the Blast this year," Agar said. "There's a really exciting mix of players in the squad and hopefully we're in a really strong position in the table when I join."

Agar, 30, was a member of Australia's victorious squad in the 2021 T20 World Cup, and has also been a Big Bash League winner with Perth Scorchers.

He has claimed 48 wickets in 47 T20Is for Australia, with best figures of 6 for 30 against New Zealand at Wellington in 2021.

"Ashton is a remarkable player with a real ability to change and win matches," John Sadler, Northamptonshire's head coach, said. "He's got a winning mindset, has played at the highest level and we're delighted to get someone of his calibre to the club."

"Hopefully he can contribute some good performances and win us some games when he joins up with us."

Agar's first game will be on July 5 and his last game will be away to Durham on July 14, at which point Raza will return for the final two group fixtures.

"We've got a real like-for-like replacement in Ashton which is great, so we're pleased with the business we've done.

"Obviously the Zimbabwe series was announced after we signed Sikandar which is a shame but we've still got him for eight games at the start, then for the last two games and we're very excited about that."