Iran, facing elimination after crashing 1-0 at home to Jordan in June, have strengthened their squad with stay-away forwards Vahid Hashemian and Khodadad Azizi, who have agreed to return to help the national cause.

"I come back to help my country," said Bayern Munich star Hashemian, known as 'The Helicopter' for his aerial strength, who is ending a three-year self-imposed exile.

Veteran forward Azizi, who helped Iran eliminate Australia in a two-leg play-off for a berth at France 98, has also put aside his differences with the national set-up.

"I have no problem with teammates and officials," said Azizi. "I have returned to serve the nation."

However Iran, gunning for a third World Cup finals appearance, face a tough task against a defence-minded Jordan coached by Egyptian legend Mahmoud Al-Gohary.

The Hashemite kingdom has shot up the FIFA rankings under Gohary, who took them to the quarter-finals at their first ever Asian Cup in July.

Meanwhile China, Japan and South Korea have notably easier tasks against minnows Malaysia, India and Vietnam.

Newly crowned Asian Cup champions Japan, the region's top-ranked team, will be confident of extending their 100 percent qualifying record in Calcutta after their 7-0 trouncing of India in June.

India's English coach Stephen Constantine, hoping to avoid another cricket score, has put a heavy accent on defence in his final training sessions ahead of Wednesday's game.

"I am doing everything I can to keep the morale high," said Constantine. "Everyone knows Japan is a much stronger side, but we want to put up a good fight before our own fans."

Asian Cup runners-up China, who also have maximum points from their first three fixtures, should continue their long march to Germany as they travel to bottom-placed Malaysia.

South Korea, who top Group 7 with two wins and a draw, travel to Ho Chi Minh City hoping to avoid a repeat of their 1-0 Asian Cup qualifying slip-up against Vietnam last year.

New coach Jo Bonfrere, under pressure to re-create the form that took South Korea to the 2002 World Cup semi-finals, was confident of overcoming third-placed Vietnam despite disappointing Olympics and Asian Cup showings.

"Vietnam is expected to focus on defending its turf. My boys have been trained to break it," said the Dutchman.

A total of 32 teams split into eight groups of four are taking part in Asia's World Cup qualifying tournament. The eight group winners advance to final qualifying next year.

War-weary Iraq, fresh from their fourth-place heroics in Athens, are aiming to keep the pressure on Uzbekistan in Group 2 as they travel to Taiwan, while Asian giants Saudi Arabia head to second-placed Turkmenistan in Group 8.