In a regulatory filing, Comcast has said it has secured just 0.21 per cent, or 3.8 million shares, of "validated acceptance" from Sky shareholders.
As a result, Comcast has extended its deadline for shareholders to vote on its current offer of $34 billion bid for 61 per cent of Sky.
The new deadline is 12pm on 12th September.
Analysts are predicting 20th Century Fox could now up its own bid for the company before its counter-offer deadline expires on 22nd September.
Comcast's offer for Sky is set at £14.75 a share and has been recommended by Sky's board. This compares with Fox's offer of £14 a share. That offer originally had the backing of Sky's board but was withdrawn after Comcast increased its offer on 11th July.