The organising committee of Euro 2016 has received no formal warnings of terror threats to the tournament but is promising unprecedented levels of security to protect fans in France.
Jacques Lambert, the president of Euro 2016 SAS, said the organisers, 10 host cities and French government were united in their belief that France can and will stage a safe and successful event.
Both he and his director general Martin Kallen urged fans to get to the grounds early, as there will be double security checks, and they reassured visitors that the 10 fan zones will be the best places to watch games on big screens.
Lambert, Kallen and UEFA's acting general secretary Theodore Theodoridis were speaking to the media at the Stade de France, where the tournament starts on Friday evening with the hosts playing Romania.
But they were speaking one day after the Foreign Office warned travelling British fans that any site linked to Euro 2016 was a potential target for terrorists.
"My message is clear: we have no knowledge of targeted, concrete threats within a stadium or other venue at Euro 2016," said Lambert. "I believe the messages that have come from a number of countries are understandably precautionary but we are in constant touch with the French security services and they are contact with their partners in Europe and elsewhere."
Security at the tournament, which runs until July 10, has been the dominant issue in France since last year's terror attacks in Paris and the recent bombings in Brussels.
The tension was ratcheted up this week when Ukrainian officials revealed they had arrested a French national trying to smuggle an arsenal of weapons back to France in order to attack 15 different sites during Euro 2016.
"We've worked hand in hand with the relevant authorities for the last four years to bring the best possible event to the fans," said Lambert. "Everybody is up to speed and nobody is unaware of what has happened in France or Europe in regards to security.
"We've had to deal with what was imposed upon us but we have wanted to stay focused on delivering the best possible Euros, regardless of external circumstances that we couldn't control.
"Yes, we've had to stiffen our security measures, and we've worked with the French government to find the most effective measures possible. But our eternal goal these last few months has been to move out of this negative spiral that we've found ourselves in."
Those stiffened measures at the stadium venues and fan zones will include two perimeters of security, the first coming before you get to the stadium gates, which may include X-ray machines for certain entrances and games.
Every stadium will be open three hours before kickoff and fans are encouraged to come early, particularly as there will be entertainment laid on at the venues, including the broadcast of earlier games on big screens if applicable.
"What is important is that fans come early -- don't leave it until the last moment," said Kallen.
On a more positive note, Kallen said there were now only 8,000 tickets remaining across the 51 games, which means more than 99 percent have been sold.
He also said new pitches had been laid in Lille, Marseille and Nice, the weather forecast was good and the last of the 24 teams to arrive, Portugal, would be in France by Wednesday.
The first big test of the security plan will come when French DJ David Guetta plays a free show at the Eiffel Tower fan zone on Thursday.
Some security experts have suggested the fan zones are the most vulnerable sites, but Lambert and Kallen said the French authorities have never considered scrapping them.
They explained that the organising committee, host cities and government met immediately after the Paris attacks last November and decided that fan zones, with proper security, were a safer option than having fans being dispersed throughout city centres.
On the subject of hooliganism, Lambert said there were some matches that French police were more concerned about than others -- Germany against Poland next week, for example -- but denied that England versus Russia in Marseille was one of them, despite what happened at the 1998 World Cup when English fans clashed with locals.
UEFA's Theodoridis dealt with the only other contentious issue: his president, Michel Platini.
The Frenchman was banned from all football activities last year for receiving a corrupt payment from former FIFA boss Sepp Blatter. He has twice failed on appeal to lift that ban, although it has been halved from eight years to four.
This means he has been forced to admit he can no longer continue as UEFA president and many wondered if he would even be allowed to attend a tournament he did so much to bring about.
But Theodoridis revealed UEFA has received "clarification" from FIFA's ethics committee to say that Platini, who is not expected at Friday's game, can attend matches in a "personal capacity" providing he has no "official role".