Tablespace resize in Oracle 10g

Question

I'm trying to resize a couple of tablespaces but the following query is only valid in Oracle 11g.

alter tablespace 2 DATAFILE '/appli2/oracle/xxx/oradata02/xxx_undo_01.dbf' resize 3g; 

In oracle v10g i try with this query, picked from oracle documentation :

alter DATABASE DATAFILE '/appli2/oracle/xxx/oradata02/xxx_undo_01.dbf' resize 3g;

I work with Oracle 10g and this query throws error message according to a non valid ALTER DATABASE modifier.

Error messages: ERROR at line 1: ORA-02140: invalid tablespace name

Thanks in advance.