The Champions League final between Manchester City and Chelsea remained without a confirmed venue on Tuesday as UEFA and the UK government remained locked in talks over Wembley or Porto in Portugal.
The final is set to be moved from Istanbul's Ataturk Stadium with Turkey in the grip of a surge in coronavirus cases and added to the UK's 'red list' of countries with the most severe travel restrictions.
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The UK government hope to move the final to Wembley due to both finalists being from the Premier League and the safety with which tens of thousands of fans can attend in England - but a considerable sticking point exists over waiving quarantine rules for visiting delegates, broadcasters and sponsors.
A final decision is expected to be made by Wednesday and UEFA is still hopeful that the issues can be resolved, but the disagreement has led Porto to become an increasingly likely option if Wembley falls through.
Portugal has recently been added to the British government's 'green list' for foreign travel, meaning travellers can visit from May 17 without having to self-isolate when they return.
Portugal are keen to host the Champions League final for the second time in as many seasons after Lisbon's Estadio da Luz held Bayern Munich's triumph over Paris Saint-Germain last year.
However, there is a sense that UEFA feels it has an obligation to the UK Prime Minister after he backed the governing body so strongly over the European Super League debacle - and Wembley is still a strong contender to stage the final.
The Turkish Football Federation has invested a lot to make the final happen safely in Istanbul, including expanding the media area and ensuring the stadium is Covid-secure.
Sources in Turkey have told Sky Sports News they would naturally be disappointed if the final did not go ahead in their city, adding UEFA cannot take the final away from the country without their agreement.
They are also sad to be placed on the UK "red list", having made the effort in good faith, but they will be reimbursed if it is moved and the country is expected to discuss a counteroffer, such as another final in a future season.
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From May 17, outdoor sports venues in England are due to be allowed up to 10,000 fans or 25 per cent capacity, whichever figure is lower. However, 20,000 have already been earmarked for the Champions League final, which would mean it would need to be run as a pilot event.
The Sky Bet Championship play-off final is currently due to take place on Saturday, May 29 at Wembley Stadium, but the EFL says it is "willing to listen to moving the play-offs" to an alternative date.
However, with the European Championships due to get underway on June 11, it would have to be played as soon as possible after the Champions League final.
EFL fans and clubs may also need to be compensated for tickets and travel already booked, and there would also likely be discussions as to whether a greater number of fans could attend if the Champions League final allows 20,000 spectators in.