SQL Server - Stored Procedure, If Exits - Delete Constaint & Tablel

Hi Experts,

I am very new to all this.

I need help this is giving me errors.

I am passing parameters from SSIS to the SP in SQL Server 2008 R2
      @fileId int,
      @TBLNM varchar(40),

That is working fine I can tell by the test I do:
      PRINT 'STARTING DELETION OF: ' + @TBLNM
      PRINT 'THIS IS THE VALUE OF FILE_ID: ' + cast(@fileId as varchar(20))


I would like to first check if a Constaint exist, if it does delete and the table.

I have this code:
      --DELETE CLAIM TABLE(S)
      PRINT 'STARTING DELETION OF: ' + @TBLNM
      PRINT 'THIS IS THE VALUE OF FILE_ID: ' + cast(@fileId as varchar(20))
      SET @rc = 1
      WHILE @rc > 0
      BEGIN
            BEGIN TRAN
            SELECT @sql = 'IF OBJECT_ID  (''dbo.' + @TBLNM + ''') IS NOT NULL  ' +
           'ALTER TABLE dbo.' + @TBLNM + ' DROP CONSTRAINT CK_' + @TBLNM + '_Max_File_ID ;' +
           ' DELETE FROM ' + @TBLNM + ' AS T' +
           ' WHERE T.[FILE_ID] = ' + cast(@fileId as varchar(20))+ ' AND
                        EXISTS(SELECT #CLAIM_TEMP.CLM_KY
                                 FROM #CLAIM_TEMP
                                 WHERE #CLAIM_TEMP.CLM_KY = T.CLM_KY AND
                                       #CLAIM_TEMP.FILE_ID = ' + cast(@fileId as varchar(20)) + ')'
                  exec sp_executesql @sql;
                  
                  SET @rc = @@ROWCOUNT
            COMMIT TRAN
      END;
      PRINT 'ENDING DELETION OF: ' + @TBLNM

      CHECKPOINT;

But it is not working correctly

Error:
"Incorrect syntax near the keyword 'AS'.".
Also would like to know if this:
'IF OBJECT_ID  (''dbo.' + @TBLNM + ''') IS NOT NULL  
Takes care of both Constaint & Table Existing

Please help and thanks...