Mr Zelensky pointed out two main reasons, including technical problems in production and sponsorship from partners is being delayed, while asserting that the orders will be completed by the end of the year.
Mr Zelensky first announced the development of Flamingo in August, introducing it as the first self-made long-range cruise missile in Ukraine, with a range of up to 3,000km.
With such a range, Flamingo could reach Moscow if launched from Ukrainian territory. Zelensky had previously warned that he would retaliate by causing power outages in Russia's border areas and Moscow.
However, some experts say Flamingo has a design quite similar to the FP-5 system introduced by defense company Milanion Group (UK - United Arab Emirates) earlier this year at the weapons exhibition in Abu Dhabi.
Meanwhile, Russian media said that the country's air defense system intercepted a Flamingo missile flying at relatively low speeds, with a Soviet-style engine and many non-Ukrainian components.
Other sources said that the fuel for Flamingo was produced in Denmark, at a facility in the south of the country operated by the FPRT company - a branch of Fire Point (Ukraine, the missile developer).
Russian Foreign Ministry spokeswoman Maria Zakharova has said that Flamingo missiles were designed with the sole purpose of " deep attack in Russian territory", and accused Denmark of supporting Ukraine in carrying out terrorist acts.
