Poland and Ukraine have been criticised for the slow progress of preparations since being awarded the tournament last year and European football's governing body UEFA is subjecting both countries to close scrutiny after suggesting the event could be moved.
But Martin Kallen, UEFA's special adviser to president Michel Platini, was upbeat on his first visit to Kiev.
"I think a lot of things have been done and there is a lot of work in front of us. But I am positive that the work will be accomplished," he told a news conference alongside the heads of the Polish and Ukrainian football federations.
"I trust fully what was guaranteed."
A dispute between the Warsaw government and the FA created further difficulties and Polish FA head Grzegorz Lato was quoted by Polish media as saying his country could host the competition with Germany if Ukraine proved unable to take on the tournament.
But he said those comments were taken out of context.
"For sure -- 100 percent -- Euro-2012 will take place in Ukraine and in Poland," Lato told reporters.
Lato was elected after the FA board was suspended on the request of the government, triggering a threat by FIFA and UEFA to take the competition away. Lato promised the government and his Association have now resolved their problems.
"I can guarantee today that that for sure until 2012 there will be no conflict between the minister and the Polish football association," he said.
Both countries have had problems building or renovating stadiums -- Kiev lost a year through legal wrangling over an adjacent shopping centre and then switched contractors.
The western city of Lviv has only started building a stadium. It chose a Ukrainian contractor after an Austrian firm pulled out last month.
Ukrainian media on Friday cited Platini repeating his threat to strip the countries of the tournament should one of them not meet the preparation criteria.
"Poland and Ukraine are well aware that it is a key condition that stadiums in their capitals be built in timely fashion.
"If they are not ready, then Euro 2012 will not take place in either Kiev or Warsaw," he told reporters at a press conference in Sofia on Wednesday.
