England have steadied the ship with some patient batting on day three of the first Ashes Test.
Cook and Pietersen forged a stubborn partnership as they put on 100 together before the latter played on to his own stumps from a James Pattinson delivery, being dismissed for 64.
Agar also claimed the wicket of Jonny Bairstow shortly after lunch when the batsman sent a thick edge into the gloves of Brad Haddin, while Matt Prior was dismissed for 31 when Ed Cowan caught him off the bowling of Peter Siddle.
Bell then passed the half-century mark as he began to form a good partnership with Stuart Broad that saw England reach the end of play without further loss.
Broad was involved in a controversial moment when he appeared to hit a delivery that carried through to Clarke, but umpire Aleem Dar somehow missed it and Broad was handed a reprieve, ending the day on 48* alongside Bell (95*).