Only POT textures can be compressed to ETC1 format even image is of size 700x1000 (divisible by 4)

I am trying to import an JPEG image for my 2D game. Texture import setting inspector complains about being it a non-POT texture. But my image size is 700 x 1000, both width and height is divisible by 4. Also I have not enabled generation of Mip Maps but still it is not able to compress it. In my other project I have images of size 768x768 or 600x360 or 700x700, all divisible by 4 and inspector does not display any compression error related message. So why it is complaining about this 700 x 1000 image? Please refer the snapshot of inspector settings.