impdp via DB Link Issue

Greetings -

I created a Dblink successfully,  but when I tried to import data remotely, I was getting the error message below. Could someone assist please.

I can access the DB remotely Ok !

SQL> select sysdate from dual@TO_RDS;

SYSDATE

-----------------

17-APR-14

But I can't run impdp remotely:

[oracle@ip-10-92-51-10 admin]$ impdp RDSUSER/passw@TO_RDS

Import: Release 11.2.0.4.0 - Production on Thu Apr 17 18:53:13 2014

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UDI-12154: operation generated ORACLE error 12154

ORA-12154: TNS:could not resolve the connect identifier specified