Need to join two tables, in sql server

Need to join two tables, in sql server

I need to join two tables, table1 has 1000 rows which has the identity
number set to ID column, similarly I have another table with 1000 rows and
it also has a ID column with identity number set to it, so now when I join
this two tables after 1000 rows of 1st table the number should start from
1001 and so on from table 2. How can I do tat, can you please help me out
in this.