An England and Wales Cricket Board (ECB) statement said: "Stephen Harmison has suffered an exacerbation of the hernia problem which he experienced during the fourth Test against West Indies at Durham.
"He will be reassessed by ECB medical staff early next week and at this stage he is rated extremely doubtful for the first Test against India starting on Thursday."
The selectors, due to announce the squad on Sunday, had their plans disrupted after Harmison aggravated his "non-serious hernia" injury while playing Friday in Durham's ongoing Championship match away to champions Sussex at Hove where he bowled just five overs.
Harmison withdrew from the remainder of the four-day game on Saturday and chairman of selectors, David Graveney, said of the quick's injury: "He will have it reassessed on Monday. At this stage he would have to be considered extremely doubtful for the first Test.
"He is not ruled out."
The 28-year-old Harmison originally sustained the injury at his Riverside home ground nearly a month ago during England's fourth Test win against the West Indies.
However, he opted against immediate surgery after being advised he could continue to play in the India series and Durham's Friends Provident Trophy final against Hampshire on August 18 - the county's first senior Lord's final.
Harmison's fitness problems increase the chances of Lancashire pace bowler James Anderson being added to the side that completed a 3-0 Test series win at the Riverside when the squad is announced.
After a wayward start to the season, Harmison took 10 wickets in the final two Tests of the West Indies series as a member of a four-man specialist attack compromising three quicks and left-arm spinner Monty Panesar.
But with pace bowling all-rounder Andrew Flintoff still sidelined with an ankle injury, England will want to be sure all their quicks are fully fit for the challenge of playing against a strong India batting line-up.
England's only other concern remains the form of batsman Andrew Strauss.
The left-handed opener did score 77 in the first innings at Riverside but this was only his second fifty in his last 17 Test innings.
In the last month his only senior cricket has consisted of two successive noughts in two Twenty20 matches for Middlesex and a 17-ball one against India while captaining England Lions, the 'A' side, in their ongoing tour match at Chelmsford, east of London.
But Strauss, putting his own form to one side, said he was confident England could give new coach Peter Moores a second successive Test series victory in his first season in charge.
"In the England team, we like to think we should beat everyone at home - and India should be no exception to that, " said Strauss.
"India are a very good Test match side, there's no doubt about that. They've always been very strong in their batting and that will remain the case."