The 31-year-old has been without a club since leaving Wolverhampton Wandererers in the summer and will provide cover for Christopher Dilo. The Frenchman is expected to be out for up to three weeks with a knee injury sustained in last weekend's win over St Johnstone. Kello, who spent four seasons at Tynecastle, has signed until January, subject to clearance, and will now battle with David Cornell, the on-loan Swansea City goalkeeper, for the right to be first-choice goalkeeper.
"Marian has a very good pedigree and we are always looking to try to improve what we have at the football club," said manager Danny Lennon. "He trained with us and is looking to get back and play at a decent level."
Jackie McNamara, Lennon's opposite number tomorrow, has praised the St Mirren manager for emerging unscathed from a difficult time but hopes to put an end to that settled spell. "They are on a decent run, with seven points out of nine," said the United manager. "After the stick Danny took, credit to him, he stuck to his guns and he proved a few people wrong. Yes, they have had a bad start to the season but looking at their games there wasn't much in it between [losing] and drawing. Sometimes that is a thin line."