ITWEENPutOnPath or PointOnPoint ana LookAt target

Hello

I try to mofidier my script of trajectory based on ITWEEN so that my object looks at a target during its travel(movement).
I have a problem with LookAt on-line 37.

error code
Assets/Camera Path pour ITWEEN avec path MAYA et regarde 1 cible.js(37,25): BCE0023: No appropriate version of ‘UnityEngine.Transform.LookAt’ for the argument list ‘(UnityEngine.GameObject)’ was found.

#pragma strict 
public var target_Path1 : GameObject; 
public var time = 10.0;               
public var Cible_a_regarder : GameObject ;     


private var tabt : Transform[];
 private var running = false; 
 private var paused = false;
 private var fraction = 0.0; 
 
 function SetPath (pathObject : GameObject){
     var id : int = 0;
     tabt =null;
     tabt = new Transform[pathObject.transform.childCount];
     for(var child: Transform in pathObject.transform)     {
            tabt[id++] = child.transform;
                 }
  WalkThePath();
                                           }
  
 
 
 function WalkThePath() {    
 paused = false;
 running = true;
 fraction = 0.0;  

  while (running) {
         transform.position = iTween.PointOnPath(tabt, fraction);
         
 if (!paused)
          fraction += Time.deltaTime / time;
 if (fraction > 1.0) fraction = 0.0; 
        var futurePos = iTween.PointOnPath(tabt, fraction + 0.02); 
        transform.LookAt(Cible_a_regarder);  
               yield;
                   } 
                      }
                   

                   
                                     
function OnGUI(){
    if(GUI.Button(Rect(290,80,100,20), "commencer"))    
    {
           SetPath(target_Path1);    
    }    
   
   
     if(GUI.Button(Rect(390,80,100,20), "Pause"))    
     {  
           paused = true;    
     }     
     
     
     if(GUI.Button(Rect(490,80,100,20), "Reprise"))    
     {
            paused = false;    
     }     
     
     if(GUI.Button(Rect(390,100,120,20), "Reculer par étape")) 
     {       
           fraction -= 0.2 / time; 
           if (fraction < 0.0) fraction = 0.0;   
     }    
     
     
     
     if(GUI.Button(Rect(510,100,120,20), "Avancer par étape")) 
     {       
           fraction += 0.2 / time; 
           if (fraction < 0.0) fraction = 0.0;   
     }    
     
       if(GUI.Button(Rect(590,80,100,20), "Stop"))    
      {
          running = false;    
      }
          }

Transform.LookAt() takes either a transform or a position. So you can call it:

 transform.LookAt(Cible_a_regarder.transform); 

Or:

transform.LookAt(Cible_a_regarder.transform.position);