"issues warning" is correct and usable in written English.
You can use it to refer to someone or something officially making an announcement that something negative might happen if certain actions are taken. For example: "The government has issued a warning that residents should stay inside due to severe weather."
UCL issues warning after student death from meningitis University College London has warned of the risks of meningitis after it confirmed a student had died from the disease, The London Tab reports.
(Reuters) MIDDLE EAST IRAN: KHATAMI ISSUES WARNING -- In one of his strongest attacks against hard-liners, President Mohammad Khatami warned of a social crisis if Iran's ruling clerics kept misusing their power to stand in the way of democratic reforms.
Page A6 PARAGUAY ISSUES WARNING TO BRAZIL Recent tensions between Brazil and Paraguay caused by Paraguayan farmers invading Brazilian-controlled farms along the countries' border were heating up as Brazilian troops began exercises in the region.
The sage of Omaha, as he has come to be known, has been on the right side of most financial issues, warning against the excesses of the dotcom boom in the late 1990s and describing derivatives as "financial weapons of mass destruction".A man renowned for stinginess in his early years has become a great philanthropist.
After more than a year of adapting Labor's traditional positions to Mr. Sharon's agenda, Benjamin Ben-Eliezer, the outgoing defense minister and Labor's chairman, chose to make a stand on social issues, warning that the budget might leave tens of thousands of poor children hungry.
Dr. Mahler was outspoken on many issues, warning about lax hygiene in airline food, fad diets, misleading drug labeling and what he called an excessive reliance "on unproved, unsophisticated and overcostly health technology". He pressured infant-formula manufacturers not to discourage mothers from breast-feeding.
