Mauritania's civilain government was elected last year
Mauritania's Islamist opposition is in the government for the first time.
The moderate Islamist National Rally for Reform and Development (RNRD) has joined the cabinet of new prime minister, Yahya Ould Ahmed Waghf.
Mr Waghf said severing diplomatic ties with Israel was not on the agenda. Mauritania recognised Israel in 1999.
Landmark elections in March 2007 saw a military junta hand over power to a civilian government. The Islamists have five MPs in the 95-member parliament.
The left-wing Union for Forces of Progress is also joining the cabinet.
But the main opposition party, Rally of Democratic Forces, has refused to join the government, although its leader, the veteran politician, Ahmed Ould Daddah, says it remains open to dialogue.
Former prime minister Zeine Ould Zeidane, who led the third largest party, resigned on Tuesday.
The new prime minister, who was formerly a university economics teacher, is president of the ruling party, the National Pact for Development and Democracy (PNDD).