Off shore, and generally off the radar, a fight is heating up between Israel and Lebanon over who controls a valuable piece of the Mediterranean that is known to have two major gas fields possibly worth billions of dollars. As always, when it comes to border issues between these two nations, the rhetoric has become heated -- and there's the fear that this could signal the next big clash between Israel and Hezbollah. Hezbollah's deputy secretary general Sheikh Naim Qassem minced no words, saying today the group "will remain vigilant in order to regain its full rights, whatever it takes."

Israel's rhetoric has been equally heated. Last year, Deputy Prime Minister Uzi Landau said Israel "would not hesitate to use our force and strength to protect...international maritime law."

Qassem's comments today were in response to Israel, which on Sunday issued a map that it plans on submitting to the United Nations. Lebanon says, though, that the Israeli map encroaches on their territory by more than 1,500 square kilometers. Last year, Lebanon submitted a map of their own to the world body -- hoping for mediation.

Israeli officials say Hezbollah, boosted by its new political clout, is trying to pick a fight with Israel as a pretext for continuing their conflict.

But Hezbollah says that Israel is trying to snatch valuable territory and that it won't be "frightened by" Israeli threats.

A resolution is tricky. There is a lot of money at stake for the two resource-poor countries -- maybe up to $90 billion worth of gas. Hezbollah's position is not dissimilar from the previous Western-backed government led by Saad Hariri, which also accused Israel of taking part of its offshore territory.

So, who actually controls what? The only internationally recognized border between Lebanon and Israel -- the blue line -- was drawn up in 2000 by the United Nations, following the Israeli withdraw from southern Lebanon.

But trying to extend that into the sea isn't so simple. Israel says it drew a straight line out from shore to demarcate the sea border. But Lebanon says the angle Israel used gives it more territory than it should have, since it's drawn too far north. The territory extends to water controlled by Cyprus (both Israel and Lebanon have separate agreements with that country).  

International law says countries that share sea borders have to reach bilateral agreements on how to demarcate them. But that's not so easy, given Israel and Lebanon are still technically in a state of war.

Israel would seem to have an advantage, legally -- since it has already staked its claim and is exploring the fields, experts say.

That's why Lebanon is asking the United Nations to step in. Though, as with everything when it comes to that world body, the process is sure to take a long time, if it's ever resolved. In the meantime, there will be more heated rhetoric. This weekend, Israel's Vice Prime Minister Moshe Ya'alon, compared the sea dispute to Shebaa Farms, the tiny area that Lebanon and Israel both claim and have led to flare-ups in the past. Given what's at stake in terms of mineral wealth, and the history of the border -- whether it stays at just heated rhetoric, or escalates to something more significant, is a question that has to be considered.