Login to WordPress from another site

Hello,

Please help. I need to know if there is a way or plugin that will allow to insert the WordPress login window to different site.

I have this client who has a landing page and wants to have that functionality.

The landing page is completely different than the WP installation, it may even be in a different server.

So you go to the landing page and you will see a username and password boxes that, when info is entered, will get you to the WP site.

Thanks for your time and help