Exporting a large table

I am getting the following oracle error message during an

	export of a very large table which is not being updated or
	queried during the process. (The table has used up about
	2 gig of database space and I think it has 10 million+ rows)

	The process lasted for 3.5 hrs and then I got the error 
	message.

	EXP-00008: ORACLE error 1555 encountered
	ORA-01555: snapshot too old (rollback segment too small)

	Any ideas how to dump this table?

	Thanks in advance.
	Hitesh Patel