Iwamasa's late heroics saw Kashima move up to 60 points, three ahead of Kawasaki Frontale and five in front of Nagoya Grampus, who have a match in hand.

Jubilo are battling to avoid relegation but they frustrated the home side for much of the contest.

The visitors appeared to have held on for an unlikely point before they conceded a free-kick near the left corner flag four minutes into stoppage time for Yuichi Komano's foul on Marquinhos.

Substitute Chikashi Masuda took a quick set-piece and picked out Iwamasa, who escaped the attentions of his marker to head past goalkeeper Yoshikatsu Kawaguchi at his near post to delight the home crowd of 29,820.

"The strong determination of our players produced this result. They kept on playing and never gave up. That attitude brought us the goal in stoppage time," said Kashima manager Oswaldo Oliveira.

Kashima midfielder Takeshi Aoki added: "It was such a tense game and you never knew which way it would go. But we didn't lose our concentration to the very end, and that helped us.

"But nothing has been decided yet. We shouldn't relax and must be prepared for our final game."

Kashima will secure their second straight J.League title and sixth overall with victory at last-placed Consadole Sapporo next Saturday.

Given their vastly superior goal difference over Nagoya, who host Consadole on Sunday, only an unlikely defeat in Sapporo next weekend would open the door to their rivals.

Kawasaki kept alive their slim hopes of winning the title with a 4-0 trouncing of Vissel Kobe.

North Korea forward Jong Tae-se opened the scoring in the fourth minute and tucked away a rebound in the 63rd minute to put the home side in control.

Juninho netted his 12th goal of the season two minutes later to make it 3-0 and after Vissel were reduced to 10 men following the dismissal of Kunie Kitamoto, Renatinho turned in a Juninho pass in the final minute to complete the rout.

Asian champions Gamba Osaka all but ended Urawa Reds' hopes of a top-three finish with a 1-0 win over the team that they beat in the semi-finals of the Asian Champions League last month.

The home side had forward Masato Yamazaki sent off shortly before the break for his second booking but Reds were also reduced to 10 men when Brazilian forward Edmilson was dismissed in the 66th minute for violent conduct.

The match looked to be headed for a goalless draw until Japan midfielder Yasuhito Endo headed home an Akira Kaji cross in the 85th minute to end Gamba's three-match losing streak.

"This is obviously not a good result at all," said outgoing Reds boss Gert Engels.

"We were not in a situation to focus on the game because of some problems we were having. But I don't see any problems the way we played today except for our finishing. We didn't have quality in front of goal."

Oita Trinita moved ahead of Urawa into fourth spot after winning 2-0 at Kashiwa Reysol thanks to second-half goals by Shingo Suzuki and Taikai Uemoto.

Shimizu S-Pulse edged relegation-threatened JEF United Chiba in a 3-2 thriller while Tokyo Verdy also remained in relegation trouble after losing 2-0 at Yokohama F. Marinos.