BORDEAUX, France — Ukraine and Poland will remain co-hosts of the 2012 European Championship, but European soccer's governing body warned they could lose the tournament if preparations fall behind schedule.

UEFA also confirmed the 2016 championship will expand from 16 to 24 teams, approved the renaming of the UEFA Cup to the UEFA Europa League and said it is looking into suspicious betting patterns from 25 lower-tier matches.

The governing organization said there has been progress in the past six months in Ukraine and Poland, but it was "neither uniform nor constant."

"Both host countries must continue to make the necessary efforts as any slackening could put in doubt the organization of this tournament in these countries," UEFA said.

UEFA president Michel Platini visited both countries in July.

"We were promised new airports and we will not have new airports," he said at a news conference. "We were promised new roads and we are still waiting. Warsaw and Kiev are the key issues. We cannot organize a European competition without the capital city."

Platini said the co-hosts promised that stadiums in Kiev and Warsaw will be ready in time.

"If we don't have the stadium in Kiev, that's a problem. Ukraine can't afford to send everyone to a country where there is no capital city (ready)," Platini said. "They are working very hard and we have confidence in them. The president and the prime minister tell me it will be ready. What am I supposed to say? That I don't believe them?"

However, Platini warned of changes if the host countries fail to meet the new expectations.

"If there are neither the stadium ready in Kiev or Warsaw, we would certainly do something different," Platini said.

UEFA said it will decide next year how many and which stadiums and cities will be used as venues, with a minimum of six and maximum of eight. The number of venues will not necessarily be the same in each country.

The expanded 2016 championship will consist of six groups of four teams. The top two from each group will advance with the four best third-ranked teams. The tournament will feature 51 matches, up from 31, and last 29 to 31 days.

Platini dismissed the notion that expansion would further tire players after a long season.

"It's just one more match, a last-16 game," Platini said. "I am sure it does not change the technical standard. It's the same."

UEFA also said it was beefing up its "early-warning system" to protect against illegal betting and match-fixing. Two additional full-time staff and four additional disciplinary inspectors will be hired.

UEFA said it is looking into irregular betting patterns surrounding 25 UEFA Cup and Intertoto games from last season and this season. A special unit will look into the matter.

Also to come next season is a new format with a newly named UEFA Europa League. The move appears to create a lower-tier version of the Champions League, with teams playing each other on a home and away basis in group stages. Under the current format, clubs only play each other once in the group phase.

The UEFA Cup has struggled in the shadow of the lucrative Champions League, which gives teams global exposure and huge television revenues.