The Iranians claimed their sixth consecutive Nations League win – a national record – and their ninth in 10 matches so far in front of their home crowd at Rezazadeh Stadium in Pool 15.

They had to battle back from behind against a Portuguese side battling hard to preserve their top-tier status for next season, as one of four challenger sides who could be demoted.

Iran eventually won 23-25, 27-25, 25-17, 25-18 to move a step closer to the final round in Chicago next month.

Earlier, France had strengthened their own final credentials when they beat Australia in three tight sets.

The French had to work hard for their seventh win of the campaign but eventually came through 25-23, 25-22, 25-22.

In Pool 14, Italy also furthered their own qualification ambitions at the expense of Serbia in front of a home crowd at PalaLido.

The Italians claimed a conclusive 26-24, 25-19, 25-22 victory, their eighth in the Nations League.

Earlier in Milan, qualification outsiders Poland and Argentina played out a five-set thriller, the Poles triumphing 25-21, 25-23, 25-27, 20-25, 19-17.

It gave Poland a sixth win in this year's competition and puts them hot on the tail of the likes of France and Russia.

Second-place Brazil host Pool 16 at Ginásio Aecim Tocantins in Cuiaba and kept pace with Iran thanks to a 25-20, 21-25, 25-19, 25-14 victory over Bulgaria, 

Russia also kept themselves firmly in the qualification places with a four set win over Germany, 22-25, 25-21, 25-19, 25-14.

United States beat Japan in Pool 13, held at Sears Centre Arena in Hoffman Estates, Illinois, in straight sets – 25-15, 25-19, 25-19.

Earlier, Canada saw off bottom-ranked China, 25-19, 25-23, 22-25, 25-17.