Japan are one win away from qualifying for their sixth consecutive World Cup after grinding out a 1-1 draw away to Iraq on Tuesday.
Yuya Osako opened the scoring early for Japan, but Mahdi Kamil equalized midway through the second half as the Group B sides shared the points in the Iranian capital.
With two games left in the Asian final qualifiers, group leaders Japan improved to 17 points, one point ahead of Saudi Arabia and Australia.
If Vahid Halilhodzic's men beat Australia at home in their next game on Aug. 31, Japan will automatically qualify for the World Cup finals in Russia. Should they fail to win against the Socceroos, Japan's fate will rest on their last qualifying match on Sept. 5 at Saudi Arabia.
"I'm a little disappointed," Halilhodzic said. "I'm not sure what happened when we conceded because there was some confusion, but we didn't give Iraq much and they managed to score."
"I told the team at halftime that we can kill off the game if we score a second but then we let one in. We were exhausted, and could not carry out the plan we had in place."
Halilhodzic's boss, Japan Football Association President Kozo Tashima, was not happy with the performance.
"We did not play well," Tashima said. "(The heat) is not an excuse. We could have potentially lost the game. We need to feel fortunate that we took a point from here."
JFA technical director Akira Nishino made it clear that Halilhodzic's job was safe, however. When asked if the Bosnian would continue to stay in charge, the former Gamba Osaka boss said, "Of course."
"Given the circumstances today, how we managed the second half, the substitutions, the tactical aspect was crucial -- and it fell apart."
With temperatures climbing above 37 C on the pitch, Japan scored the first goal of the match they sorely needed in the eighth minute through Osako.
Keisuke Honda, wearing the captain's armband on his 31st birthday, swung in a corner from the right for Osako, whose back header from the near post landed into the net.
Shortly before the half-hour, Osako thought he had won a penalty when he was blatantly brought down in the box by Rebin Ghareeb. But no whistle was heard from referee Ming Fu, Osako livid at the official's lack of decision-making.
Japan managed to take the lead into the break, but the second half tested them to their physical limits as the heat began to take its toll.
Yosuke Ideguchi, who made his first start for Japan in only his second cap after Hotaru Yamaguchi was ruled out by injury, went down on the hour with what appeared to be a concussion. He had to be replaced by Yasuyuki Konno.
Then as forward Yuya Kubo and defender Hiroki Sakai began hobbling, the Iraqis took advantage in the 73rd minute.
Alaa Abdul Zahra slipped a through ball inside the area, forcing goalkeeper Eiji Kawashima and Maya Yoshida to collide into each other while attempting to clear.
The ball spilled into the path of Kamil, who slotted home into the bottom right corner to even the score, denying the visitors all three points.
Both Honda and Osako lamented the fact that Japan could not net a second goal.
"While we did well in some aspects given the inexperience and injuries we've had, we struck first so we should have managed the game better as a team," Honda said.
"It doesn't matter who we get next because it won't be easy. We need to treat our last two games like they're both a cup final."
Added Osako, "We can't make any excuses. This game exposed us in the sense that after we scored, we dropped back and weren't aggressive enough in trying to score a second."
"We just have to win now. We're at home next, and it will be the biggest game yet."
In another Group B game, last-place Thailand drew 1-1 at home to the United Arab Emirates, who are on 10 points and will need a minor miracle to qualify for the World Cup.
In Group A, Iran became the first of 32 teams to punch their ticket to Russia after beating Uzbekistan 2-0 at home on Monday.