KUALA LUMPUR (Reuters) - Malaysia on Friday reversed a pledge to ratify a UN convention against racial discrimination, following backlash from groups who fear it could dilute privileges for majority ethnic Malays.

Leaders of Islamist party PAS, former ruling party UMNO and conservative groups plan a rally next month against the convention, which they fear could strip away Malay privileges and threaten Islam’s position as the official religion.

The government will not ratify the International Convention on the Elimination of All Forms of Racial Discrimination (ICERD), the office of Prime Minister Mahathir Mohamad said in a statement, without giving a reason for the decision.

Mahathir’s ruling coalition has struggled to woo ethnic Malays after its spectacular election win in May on the back of overwhelming support from minority ethnic Chinese and Indian voters.

“The government will continue to uphold the federal constitution, which enshrines the social contract agreed by representatives of all races,” it said in the statement.

Malaysia’s ‘social contract’ was a pact made by the leaders of its Malay and minority Chinese and Indian ethnic groups regarding their rights and privileges as citizens, prior to independence from colonial ruler Britain in 1957.

The country adopted an affirmative action policy that benefits the Malays, who form 60 percent of a population of about 32 million, after deadly race riots in the late 1960s.

Ethnic Chinese are estimated at 23 percent and ethnic Indians comprise about 7 percent, government data shows.

In September, Mahathir told the United Nations General Assembly Malaysia would ratify all the human rights conventions left for it to adopt, a total of six, including the racial discrimination measure.

“Muslims, the religious, the bumiputera and all races must unite to oppose the ICERD agenda, because its concept is not based on religion or humanity,” said PAS leader Abdul Hadi Awang, using a term commonly employed to assert Malay privileges.

“Do not be influenced by the West that has abandoned religion and the ethics of true humanity,” he said on his Facebook page on Thursday.

About 30 percent of Malay voters backed the ruling party in the May 9 general election, independent polling firm Merdeka Center found in a study of voting patterns published in June.

The long-ruling Barisan Nasional coalition, led by the United Malays National Organisation (UMNO), received about 40 percent of Malay votes while PAS was backed by up to 33 percent, it said.