Natively accessing Android's KeyStore's keys in Flutter doesn't prompt for authentication

Question

I am developing an Android application in Flutter for which I need to generate a private-public KeyPair through Android's KeyStore (not simply store values in KeyStore but use KeyStore itself to generate these keys). I want these keys to be protected with biometrics/device credentials and for the KeyStore to ask for authentication when using these keys for signing.

Since flutter's secure storage doesn't provide key generating, I am using native code for generating keys through Android's KeyStore.

Native code chunk in MainActivity.kt creating these keys is:

val generator = KeyPairGenerator.getInstance("EC", "AndroidKeyStore")

generator.initialize(KeyGenParameterSpec.Builder("xxx", KeyProperties.PURPOSE_SIGN)
            .apply {
                 setUserAuthenticationRequired(true);
                 setUserAuthenticationParameters(
                    0,
                    KeyProperties.AUTH_DEVICE_CREDENTIAL or KeyProperties.AUTH_BIOMETRIC_STRONG
                 );               
            }
            .setAlgorithmParameterSpec(
                ECGenParameterSpec("secp256r1")
            ).setDigests(
                KeyProperties.DIGEST_NONE,
                KeyProperties.DIGEST_SHA256
            ).build())

var keyPair = generator.generateKeyPair()

This part works fine, keys are generated and stored in KeyStore. However, when I try to use these keys for signing, I get the following exception:

org.bouncycastle.operator.RuntimeOperatorException: exception obtaining signature: android.security.KeyStoreException: Key user not authenticated

I would like to be prompt to authenticate rather then simply get this exception. Is there a way to make natively called code to ask for authentication when accessing keys in KeyStore?