In May, it was revealed that the EFL, formerly known as the Football League before a rebrand this summer, could expand to include a fifth tier by 2019-20, with 100 teams over five divisions.
It is planned that additional clubs would come from the National League.
EFL clubs met to discuss the proposals for the first time on Thursday.
The exclusion of extra 'non-English' clubs from the plans, which will be voted on by all clubs in June 2017, would appear to remove any prospect of Scottish giants Celtic and Rangers being involved in the EFL in the forseeable future.
"The logical place for many was to source the additional teams for League Three from the National League," EFL chief executive Shaun Harvey said.
"We will now continue our consultation with the National League with a little more certainty as to what any change could mean for them."
This season, the Checkatrade Trophy has included under-21 teams from Premier League and Championship clubs for the first time on a trial basis.
More to follow.
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Premier League B teams and 'non-English' clubs will not be included in plans to reform the structure of the English Football League.