This was a battle of the top two in the standings and all three sets went to the wire at Ghadir Arena in Urmia.

Iran won 25-20, 26-24, 25-23 to assert their dominance at the top with an eighth victory from nine matches.

The other game in Pool 11 saw Poland beat Canada in four sets, 25-20, 25-27, 25-20, 28-26.

It was the Poles' fifth win of the competition and boosted their hopes of reaching the final round in Chicago next month.

Brazil, meanwhile, are up to second after a straight sets victory over Pool 9 hosts Portugal at Multiusos de Gondomar.

The Brazilians won 25-19, 25-21, 25-18 to match Iran on eight wins.

The other game in Pool 9 saw Serbia beat China in four sets, 25-17, 25-22, 25-27, 25-18.

It is a fifth win of the Nations League for Serbia, but leaves China last in the standings with only one victory from nine matches.

Elsewhere, France suffered another damaging defeat at Palais des Victoires, Cannes, losing in four sets to the United States.

France had been joint leaders alongside Iran, Brazil and Russia, but a shock loss to Argentina was followed by a 23-25, 25-22, 28-26, 27-25 reverse against the US.

The French are now fourth in the overall standings, while the US are sixth, but as hosts are guaranteed a final-round spot regardless.

The other game in Pool 12 saw Argentina win in five sets against Germany, earning their second triumph of the weekend following a surprise win over France.

Argentina won 25-19, 23-25, 23-25, 25-23, 15-10.

Pool 10, at the Palace of Culture and Sports in Varna, Bulgaria, saw Japan beat Australia 25-18, 25-27, 23-25, 25-22, 17-15 in an epic battle.

Italy beat Bulgaria 25-14, 25-20, 23-25, 25-21 in the late game.