President Jacob Zuma is "applying his mind" on the possible appointment of Constitutional Court judge Mogoeng Mogoeng as South Africa's next chief justice, his spokesperson Mac Maharaj said on Wednesday.

Maharaj said there was no time frame for a public announcement on his decision, as some NGOs kept up their campaign to not have Mogoeng appointed.

The Nobel Women's Initiative on Wednesday joined organisations urging Zuma to withdraw his nomination, the Sonke Gender Justice Network said.

Members of the Nobel Women's Initiative who are also Nobel laureates, feel that Mogoeng's many rulings undermined women's rights, and were at odds with values enshrined in the Constitution, Sonke spokesperson Mbuyiselo Botha said.

Laureates, Jody Williams, Shirin Ebadi and Mairead Maguire joined Sonke, Section 27, the Treatment Action Campaign and the Lesbian and Gay Equality Project in the call.

The latter organisations said on Wednesday they also plan to submit a further letter to Zuma, reiterating their concerns.

They objected to past judgments handed down by Mogoeng which they feel show problems with his approach to gender violence, specifically violence against women and children.

They believe the Judicial Service Commission made a mistake by recommending Mogoeng for the job, after his public interview in Cape Town last weekend.