UPDATE 1-S.Africa's Marcus-no desire to intervene in FX mkt

* Marcus says cbank won't target currency level

* Marcus questions viability of FX intervention

* "Ready and willing" to discuss cbank mandate (Adds details, background, quotes)

By Wendell Roelf

CAPE TOWN, Nov 19 (Reuters) - South Africa's central bank Governor Gill Marcus said on Thursday the bank had no duty or desire to intervene in the currency market and it was only active to build its reserves.

"There is no exchange rate that is a perfect rate, and it's not the bank's task or desire to intervene ... in the markets to achieve a particular rate of exchange," Marcus told parliament's finance committee.

"If you want to intervene people will take you on, that is the lesson of the world and, therefore, we do not look at a particular rate, we do not intervene to achieve a particular rate. We look at the opportunities in the market ... to build reserves," she added.

The rand has gained more than 20 percent against the dollar this year, raising concerns that its gains would weigh on sectors such as manufacturing. It lost ground on Thursday, though, dipping more than 1.5 percent as the dollar firmed.

The central bank has steadily lifted reserves over the past five years after it brought a long-standing negative position into balance in 2004. Its net reserves rose 2.3 percent to $38.784 billion in October, due to a jump in currency holdings and a higher gold price.