James Mclean's second-half goal sent Ireland through to the playoffs at the expense of Wales while Iceland build on Euro 2016 success with first World Cup appearance.
Coleman to consider options after Wales heartbreak, joy for Iceland and Serbia: 2018 World Cup qualifying round-up
Wales manager Chris Coleman said he would "let the dust settle" before deciding whether to continue after his side's 2018 World Cup qualification hopes ended in a 1-0 defeat by Ireland on Monday.
Coleman led Wales to the semi-finals of the 2016 European Championships but his dream of taking the nation to their first World Cup finals since 1958 was crushed in the Cardiff City Stadium.
James McClean's second-half goal meant Ireland claimed a play-off spot after they leapfrogged Wales into second place in Group D behind Serbia.
It was Wales' first defeat in a World Cup qualifier for 12 games and their first home defeat in a competitve fixture for four years -- a record Coleman said he was proud of.
"All I can think about right now is the faces of the players in the dressing room and their disappointment," said Coleman, who took over in 2012. "They are inconsolable but they should be very proud.
"I will take some time to let the dust settle, we will sit down and have a chat and take it from there.
"This was our first defeat at home for four years. Four years ago we were playing against Macedonia in front of 8,000. It is different now."
Ireland will probably face one of the seeded nations in the playoffs, possibly Portugal or Italy, but showed in Cardiff that they will be no pushovers, whoever they draw next Tuesday.
"We are in the playoffs. Whenever the draw is made we will take our chance," Ireland manager Martin O'Neill said.
"The impression of our campaign? Absolutely delighted. When the draw was made I thought we had a very difficult group. We have come through, fantastic."
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Struggling Italy head for playoffs
Italy battled to a 1-0 win over Albania with a late Antonio Candreva goal as the struggling Group G runners-up head for the playoffs in a bid to reach next year's World Cup.
The four-time World Cup winners had already clinched a play-off spot by finishing second behind group winners Spain, but, after a humiliating 1-1 draw at home to Macedonia on Friday, they were under pressure to perform in Albania.
Italy squandered several good chances until Candreva, unmarked to the left side of goalkeeper Etrit Berisha, was found with a ball across the area from Leonardo Spinazzola and fired home a powerful shot to give Italy the victory.
“We played a great game, were united in our play and we brought the victory home," said midfielder Lorenzo Insigne. "Today we sought the victory at all costs and we managed to win. We gave everything and showed that Italy never gives up.”
Iceland reach first World Cup
Less than 18 months after sensationally knocking England out of Euro 2016, Iceland qualified for the World Cup for the first time following a 2-0 win over Kosovo.
Needing victory to guarantee top spot in Group I, goals from Everton's Gylfi Sigurdsson and Johann Gudmundsson ensured Iceland would be on the plane to Russia 2018.
"I thought after Euro 2016 that the hardest thing would be to motivate ourselves again," said Iceland manager Heimir Hallgrimsson.
"The hardest thing was to get going again after our massive party in France. And what's more in a group contested between Croatia, Turkey, Ukraine and Finland, who are much better than their position in the group would have you believe.
"The success is not an end in itself but a long journey towards a final destination."
Serbia through after Georgia win
Belgrade was gripped by anxiety before an overwhelming sense of joy and relief greeted Serbia reaching the World Cup with a nerve-jangling 1-0 home win over Georgia, thanks to substitute Aleksandar Prijovic's 74th-minute goal.
The result, celebrated ecstatically in the cauldron of Red Star's Rajko Mitic stadium, left the Balkan nation top of Group D with 21 points from 10 games, two more than second-placed Ireland.
"I expected a tough game against Georgia and suspected that the final step would be the most difficult," Serbia manager Slavoljub Muslin told a news conference after the organisers set off spectacular fireworks which rocketed into the night sky over the Serbian capital.
"Georgia were the better side in the first half and I told the players to move up a gear after the break, though we had to keep it tight at the back too."