* Main opposition boycott holds as campaigns start
* Talks continuing to end deadlock
By Vincent Fertey
NOUAKCHOTT, May 21 (Reuters) - Campaigning for Mauritania’s first presidential election since last August’s military coup began on Thursday, boycotted by all opposition candidates with a real chance of unseating junta chief Mohamed Ould Abdel Aziz.
Abdel Aziz, a presidential guardsman at the time, overthrew the Saharan Islamic state’s first freely elected leader in a bloodless takeover. He is widely expected to cruise to victory in a June 6 poll that major opposition parties have snubbed in protest at the electoral timetable set by the military junta.
Fully-contested elections would bestow greater international legitimacy on the next president of the iron ore-producing nation, but international efforts to broker a solution to the deadlock appeared to have failed.
Opposition coalition the National Front for the Defence of Democracy (FNDD) has refused to participate in the elections, while the military junta has shown no sign of willingness to postpone the vote in order to ensure opposition involvement.
"The real question is, who will be seen as to blame if the mediation comes to nothing," said a European diplomat in the capital Nouakchott of how the wider world will view the vote.
The African Union imposed sanctions against Mauritania in February while the European Union declared last month it could not work with the junta and said it would suspend aid. The absence of EU election monitors would be a blow to Abdel Aziz’s efforts to win recognition for the election result.
Still, Abdel Aziz has delayed his own campaign while the mediation talks continued.
"It is a unilateral decision I have taken to put back by 24 hours the start of my campaign to encourage the negotiating parties to find a solution," Aziz told journalists late on Wednesday.
"YES WE KANE"
In his absence, the few opposition figures who have registered as candidates stole the limelight in lively and well-attended pre-dawn campaigning on Thursday.
Kane Hamidou Baba, who was thrown out of his party the Assembly of Democratic Forces (RFD) for his conciliatory stance towards the junta, is attempting to garner the youth vote.
His campaign slogan "Yes We Kane!" echoed Barack Obama’s rallying cry of "Yes We Can!" on his march to the White House last year, though observers do not expect fringe figure Baba to emulate Obama’s success.
Ibrahima Moctar Sarr, leader of the Alliance for Justice and Democracy-Movement for Renewal party, which appeals to the black population of a country that straddles black and Arab Africa, called for national unity.
"Mauritania has enormous potential. Its problem is not one of economic development, its real problem is the coexistence of people who are divided by racial discrimination," he said.
Ethnic tensions between Mauritania’s black population, which makes up around 30 percent of its 3 million people, and its lighter-skinned Arabs are a continuing concern.
Sarr came fifth in 2007 elections won by Sidi Mohamed Cheikh Abdallahi, who has been in his home village of Lemden, 200 km (125 miles) from Nouakchott, since the Aziz-led military junta released him from house arrest last December.
(Writing by Daniel Magnowski; Editing by Giles Elgood)