Uefa were forced to suspend Euro 2020 for 12 months due to the devastating impact on football of the Covid-19 pandemic.
The Premier League season resumed in June following lockdown - but all games took place behind closed doors.
The new season has kicked off again with the same measures in place and the recent spike in the virus has seen the Government extend the ban on supporters attending matches until March at the earliest.
It remains to be seen if fans will be allowed to attend all the Euro 2020 games, with Wembley scheduled to host the semi finals and final in July.
But Southgate fears the tournament might not be staged at all - leaving his plans to conquer Europe on home soil in tatters.
He said: "I think what is possible and what looks possible is going to have changed frequently over the next few months.
"We honestly don't know. You couldn't stand here with any certainty and say the Euros will take place next year. You couldn't stand here with certainty and say it is going to take place in the format it is expected to."
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One option being considered by Uefa bosses is to hold the tournament in just one or two countries, instead of 12 as originally planned.
Southgate reckons England would be one of the best options if this scenario unfolded and he added: "The indications are that towards Spring things might look a bit brighter - and I think generally those predictions have been fairly accurate.
"But we would definitely be capable of hosting, we are due to host a lot of games at Wembley anyway, so I don't think that will change.
"But it really is an unknown, what the format might end up looking like. It is impossible to predict and we have to be ready to adapt to whatever is thrown our way."
Meanwhile, Covidiots Tammy Abraham and Jadon Sancho have rejoined the squad at their Pennyhill Park base in Bagshot and will be tested along with all their team-mates and coaching staff, ahead of Sunday's game with Belgium.
But Ben Chilwell has remained at home after telling England medics he feels unwell - and will not be considered for the clash.