By Michelle Nichols

UNITED NATIONS, Sept 15 (Reuters) - U.N. peacekeeping chief Herve Ladsous said on Wednesday South Sudan's government had not taken any action on a pledge it made 10 days ago to cooperate on the deployment of more United Nations troops in a bid to avoid a possible arms embargo.

During a U.N. Security Council visit to South Sudan earlier this month, President Salva Kiir agreed to accept 4,000 extra peacekeepers and to allow some 12,000 peacekeepers already on the ground to move around freely so they can protect civilians.

Ladsous told reporters after briefing the Security Council on Wednesday the agreement "has not been enacted upon at all."

In the wake of heavy fighting in South Sudan's capital Juba in July, the 15-member council last month authorized a regional protection force as part of the U.N. peacekeeping mission and threatened to consider an arms embargo if Kiir's government did not cooperate or stop hindering the movement of peacekeepers.

"The members of the Security Council call on the government to abide by the commitments it made and to translate them into concrete steps immediately," the body said in a statement on Wednesday.

The council also expressed concern at "subsequent statements by certain members of the government which appear to contradict the commitment made to the Security Council consenting to the deployment of the regional protection force."

Britain and France believe an arms embargo should have already been imposed on South Sudan. U.S. Ambassador Samantha Power said Washington will support an embargo if Kiir's government does not implement its commitments.

However, Russian Deputy U.N. Ambassador Petr Illichev warned that such a move could harm attempts to bring peace and believes the South Sudanese government should be given at least a month to start fulfilling its pledges.

U.N. peacekeepers have been deployed in South Sudan since 2011, when the country gained independence from Sudan.

Political rivalry between Kiir and opposition leader Riek Machar sparked a civil war in 2013 but, while the pair signed a shaky peace deal a year ago, fighting has continued and Machar fled the country after the eruption of violence in July.

"The members of the Security Council expressed deep concern that members of civil society had been targeted in the days following the Security Council's visit to South Sudan," said the body, calling for the perpetrators to be held to account. (Reporting by Michelle Nichols; Editing by Paul Tait)