The move comes after complaints about drink-related disorder in the Plains Farm, Silksworth, Doxford Park and Farringdon area.
So far 10 off-licences in the areas have pledged not to sell booze to people under 21 on Friday and Saturday.
Northumbria Police are urging a further nine off-licences in the area to sign up to the challenge 21 campaign.
It is illegal for those aged under 18 to purchase alcohol.
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