I assume you are here on a non immigrant visa. In that case your chances of getting into a MST program funded by NIH are zero since they require citizenship or permanent residence. Howver, many programs have private contributors which do allow the funding to go to international students. It depends on the program and the best thing to do is go trough the ones you are interested and see what they require. Generally, you will have a much harder time getting into a program though since spots for international students are even more limited than MD/PhD slots in general.