MS ACCESS ADO SQL QUERY - SYNTAX ERROR IN UPDATE STATEMENT

experts,

what am i doing wrong???

getting syntax error in update statement....


procedure TForm1.Button1Click(Sender: TObject);

var

crud:string;
result:string;

begin

crud:='1';
result:='300';

ADO.Close;
ADO.SQL.Clear;
ADO.SQL.Add('UPDATE clients SET ');
ADO.SQL.Add('total left = :P_STS' );
ADO.SQL.Add('WHERE clientid = ' + QuotedStr(crud));
ADO.Parameters.ParamByName('P_STS').value := result;
  ADO.ExecSQL;