Development: On 3 May Peru's politicians and commentariat hailed the agreement on the maritime border with Ecuador.

Significance: It is notable, however, that Ollanta Humala, the left-wing nationalist and strongly anti-Chilean candidate for the presidency, refused to comment directly on the agreement. He said that he wanted to discuss the agreement with the foreign minister before stating his views. Peru's line is that the agreement with Ecuador reinforces Peru's case in its maritime border dispute with Chile, which is currently before the International Court of Justice (ICJ) at The Hague. Peru argues that the agreement upholds its contention that the 1952 and 1954 maritime agreements with both Chile and Ecuador did not define the maritime border but only pertained to fishing rights. Peru claims that it has now negotiated a fresh agreement, admittedly based on the 1952 and 1954 fishing accords, but the new one has the force of a treaty and thus overrides those of the 1950s.

Key points:

• Chile dismisses Peru's argument. Hernán Larraín, a prominent senator from the Unión Demócrata Independiente (UDI) - part of the ruling alliance - said that Peru's agreement with Ecuador was a "huge own goal". There are several arguments for this view. The first is that Peru did not negotiate with Ecuador: Peru simply accepted Ecuador's own map of the maritime border. Peru implies that it had been working behind the scenes with Ecuador on the map but Ecuador denies this. If this is so, Peru is effectively accepting that the 1952 and 1954 agreements define the maritime border, which is Chile's contention.

• The second argument against Peru's case is that the maritime border with Ecuador runs along a line of latitude (at a right angle to the coast). This is Chile's view of the angle of its maritime border with Peru. Peru, on the other hand, argues that the maritime border with Chile should continue into the sea at the angle at which the land border between the two countries reaches the coast. As the angle is at about 35 minutes past (on a clock face), Peru would gain a lot more sea than if the border were to run at a right angle (or 45 minutes past).

• The fascinating question is the timing of Peru's announcement of the agreement with Ecuador. The Peruvian government's line is that the agreement means that Ecuador won't be drawn into supporting Chile (its traditional ally) against Peru at the ICJ. Ecuador agrees with this point, but also implies that Peru was misguided in taking its border dispute with Chile to the ICJ.

• The timing is particularly interesting because the second round of Peru's polarising presidential election will take place on 5 June. The second round pitches Humala against Keiko Fujimori, the daughter of the now jailed former president Alberto Fujimori (1990-2000), who went to war with Ecuador in 1995 over a highlands border dispute.  

• Humala, who has toned down his anti-Chilean rhetoric from the levels it reached in his first run at the presidency in 2006, could be tempted into saying something rash, which could cost him the election. Humala is narrowly, but clearly, ahead in the opinion polls. Before the election campaign started, President Alan García made it clear that he did not want to be succeeded by Humala. The Peruvian establishment is alarmed at Humala's left-wing populism, even though Humala says that his political model, now, is former president Lula da Silva of Brazil (2002-2010) and not Hugo Chávez of Venezuela.

Pointer: The next move in the long-running process at the ICJ will be Chile's rebuttal of Peru's response to Chile's initial argument. This is due on 11 July. Then, the ICJ may move to hearing oral arguments. Peru's foreign minister, José Antonio García Belaúnde, does not expect a decision from the ICJ until 2012 or 2013.