NAIROBI - Kenya's fight to hold on to potentially lucrative Indian Ocean oil and gas reserves, threatened by a maritime border spat with Somalia, goes before the UN's top court in The Hague on Monday.

The hearings, due to last through the week, are the first stage in Kenya's battle against a 2014 claim by Somalia for the redrawing of the sea border, a move that would affect three of Kenya's 20 offshore oil blocks. A relative newcomer to the oil industry but one seen as having major potential, Kenya has awarded the three oil blocks to Italy's EniSpA.

"I'm confident that we will win that case," Somali President Hassan Sheikh Mohamud said on state radio Sunday in Mogadishu. Leading Kenya's delegation to the International Court of Justice (ICJ) is attorney-general Githu Muigai, who for his part reiterated that Nairobi "contested the jurisdiction of the ICJ to hear the matter."

At the heart of the dispute is how to draw the line of the sea boundary. Somalia, which lies north of Kenya, wants it to continue along the line of the land border, in a southeast direction.Kenya wants it to go in a straight line east, along the parallel of latitude, giving it more sea territory. The disputed triangle of water stretches over more than 100,000 square kilometres (40,000 square miles) believed to hold valuable deposits of oil and gas in a part of Africa only recently found to be sitting on significant reserves.

The Kenyan side argues it has exercised uncontested jurisdiction over the disputed sea boundary since 1979, when it proclaimed its Exclusive Economic Zone. It insists also that it had previously agreed with Mogadishu to resolve the spat through talks, not through legal action.

"In 2009 the two parties agreed to delimit the maritime boundary by negotiation, and not by recourse to the Court," Muigai said in a statement.

But Somalia has told the court that diplomatic negotiations "have failed to resolve this disagreement."

This week's hearings by the ICJ, set up in 1945 to rule on disputes between United Nations members, in fact will deal with Kenya's objections to the court's jurisdiction to rule on the matter.