Lee Clark guided Huddersfield to a 43-game unbeaten run, but has been out of work since his surprising sacking from Huddersfield Town in February.
Huddersfield dismissed him when the club were fourth in the League One table.
He is expected to sign a one year rolling contract with Birmingham.
Clark guided Huddersfield to third place in League One in 2010-11, only for them to suffer a comprehensive defeat in the play-off final against Peterborough at Old Trafford.
The Terriers won last season's play-off final to gain promotion to the Championship under the management of Simon Grayson, who acknowledged the major role Clark had played in the success.
NEWCASTLE UTD FIXTURES - 2012/3
Saturday 18th August 2012
Newcastle United v Tottenham Hotspur 15:00
Saturday 25th August 2012
Chelsea v Newcastle United 15:00
Saturday 01st September 2012
Newcastle United v Aston Villa 15:00
Saturday 15th September 2012
Everton v Newcastle United 15:00
Saturday 22nd September 2012
Newcastle United v Norwich City 15:00
Saturday 29th September 2012
Reading v Newcastle United 15:00
Saturday 06th October 2012
Newcastle United v Manchester United 15:00
Saturday 20th October 2012
Sunderland v Newcastle United 15:00
Saturday 27th October 2012
Newcastle United v West Bromwich Albion 15:00