Sunday's 2-0 home defeat to Torino was the Bianconeri's fourth defeat in their last six league games and dropped the Friulian outfit to 15th place in Serie A.
"I would like to confirm the club's absolute and unconditional confidence in our coach Francesco Guidolin," Giaretta told the club's official website.
"The loss against Torino was unexpected considering our recent good performances (against Napoli and Juventus).
"We need to reassume our provincial mentality and understand that our only aim this season is to defend our Serie A status."
Despite a solid performance, Udinese lost 1-0 at Juventus before holding high-fliers Napoli to a 3-3 draw earlier this month.
Udinese are just four points clear of the drop zone and end the calendar year at Livorno on Saturday.
"The game at Livorno is very important," Giaretta said. "It will be vital for us to not lose that game."
Udinese have won just one - they beat Sassuolo 2-1 on October 30 - and lost six of their eight games away from home this season.