Error running DBMS_STATS

We have a "legacy" database where our main user (that handles DB Administration) has an underscore in the name (for example: _USER_).  Also..our tables are named accordingly (for example _MYTABLE_).

I'm trying to run DBMS_STATS using these:

EXEC DBMS_STATS.delete_table_stats('_USER_', '_MYTABLE_')

This isn't working...I get:

ERROR at line 1:

ORA-20001: _MYTABLE_ is an invalid identifier

I also tried:

EXEC DBMS_STATS.delete_table_stats("_USER_", "_MYTABLE_")

I get:

ERROR at line 1:

ORA-06550: line 1, column 37:

PLS-00201: identifier '_USER_' must be declared

ORA-06550: line 1, column 7:

PL/SQL: Statement ignored

Any suggestions on how to get this to run?