European soccer leaders have told teams to plan for a return to action in July and August and issued a threat by suggesting leagues that cancel the season face the risk of their teams being barred from the Champions League.

The details of the next steps to deal with the fallout from European soccer seasons frozen in time by the coronavirus are contained in a letter reviewed by The Times. They provide a degree of much-needed clarity and coordination for an industry scrambling for solutions to the first stoppage of its kind since World War II.

The letter, signed by European soccer’s governing body UEFA and two powerful lobby groups representing the interests of the continent’s top leagues and clubs, makes clear that as things stand all efforts must be made to complete the frozen-in-time seasons.

Competitions that do not exhaust all options to reach a conclusion were warned there were likely to be consequences.

“Any decision of abandoning domestic competitions is, at this stage, premature and not justified. Since participation in UEFA club competitions is determined by the sporting result achieved at the end of a full domestic competition, a premature termination would cast doubts about the fulfillment of such condition,” said a portion of the letter issued late Thursday evening and sent to all of UEFA’s 55 national soccer federations and the members of the European Club Association and European Leagues body.

The letter came hours after the Belgian league announced that it had decided, subject to board approval, to cancel its competitions. The Dutch national federation earlier this week appeared to set its own date for when the current domestic calendar must be completed, making Aug. 3 the cut off.

On Friday, UEFA’s president Aleksander Ceferin, expressed frustration by unambiguously spelling out the consequences for those that abandon league championships.

“Solidarity is not a one-way street,” he told German public broadcaster ZDF. “The Belgians and any others who might be thinking about it now are risking their participation in European competitions next season.”

Ceferin added that the leagues must be completed by the end of August, and could not be stretched into September or October.

The disruptions mean the season could go well past June 30, the day in the soccer calendar when one season officially ends and another begins. The consequences of playing through that date are multiple and complicated not least by player contracts being registered to begin and end within that framework. FIFA has said it will be redrafting regulations to meet the new reality, but needs good will on all sides to cut through a thicket of legal entanglements.

The Premier League alone is facing a bill of near $1 billion to broadcasters if it fails to play the remainder of the season.

The letter, though, does provide more clarity about the direction the industry is looking to move amid daily speculation fueled by nervous executives and sports media. There have been suggestions of voiding entire seasons or deciding final places based on current standings, even though for many leagues there is about a quarter of the campaign remaining. Those games would normally determine not only the final places but also the short-term financial future of the clubs. For instance, qualification for the Champions League can be worth as much as 100 million euros to some teams, and relegation and promotion between tiers can lead to a triple digit swing in revenues, too.

In Belgium, Brugge is 15 points clear in the championship with one regular-season game and playoffs to go. Still, with the league announcing Brugge would be champions subject to the approval of its General Assembly on April 15, the team could be denied a potentially lucrative place in the Champions League should UEFA decide to take action.

The Belgian league issued a statement on Friday, saying it held talks with UEFA over its stance. Officials, it said, called for a flexible approach to the crisis that takes account for the specific situation facing each league. In Belgium, the league has already received its full payment from broadcasters.

In England, there has been criticism directed at some clubs who favor calling the season off, and starting again next season, with critics of the move suggesting they were motivated by self-interest. West Ham, a London club just outside of the relegation positions in the Premier League, are among those to have floated the idea. A column penned in U.K. tabloid The Sun by its vice-chairman Karren Brady received opprobrium when it was published last month.

“There is no dodging the possibility that all levels in the EFL, as well as the Premier League, will have to be canceled and this season declared null and void because if the players can’t play the games can’t go ahead,” Brady wrote.

A day later, UEFA on March 17 announced it had postponed its quadrennial European Championship in order to provide more space for league play to return.

“It is of paramount importance that even a disruptive event like this epidemic does not prevent our competitions from being decided on the field, in accordance with their rules and that all sporting titles are awarded on the basis of results,” Thursday’s letter said. “As responsible leaders in our sport, this is what we must ensure, until the last possibility exists and whilst planning, operational and regulatory solutions are available.”

Concrete plans, the group said, are being worked out, with a definitive agenda set to be released in the middle of May. Currently UEFA is planning for domestic games to return in July and August, with the current Champions League and Europa League seasons to recommence once those seasons have been completed.

With little sign of the restrictions on movement and mass gatherings in much of Europe being lifted in the near future, plans are being made for many of those games to be played without fans. Clubs have had to devise fitness programs for players to work out at home and even when they are allowed to return, they will have to maintain strict sanitary conditions. Some teams, like Borussia Dortmund of Germany, have allowed players back but have limited their practice to training in pairs, while others are making contingencies to deep clean buses and planes that may be used and have told players that should they return they may not be able to wash together at club facilities.

“We are confident that football can restart in the months to come — with conditions that will be dictated by public authorities — and believe that any decision of abandoning domestic competitions is, at this stage, premature and not justified,” said the letter signed by UEFA president Ceferin, European Club Association chairman Andrea Agnelli and Lars-Christer Olsson, president of the European Leagues group.