Apply for TN while OPT is pending

Hi there,
I am a Canadian citizen and had recently completed my Master's degree in the US. I applied for OPT in July and got a job offer as a dietitian last week (September). Since I likely won't get my OPT until mid- or late-Oct and I am expected to start working soon, I am considering getting TN instead. If I am getting TN, can I simply go to the border now and have it processed? Or I won't be able to get TN since my OPT application is still pending?
I learned that I may change my status by filing I-129, but would that take a long time? I am running out of time. I need to start my job soon. Any help is appreciated.

Thanks!!
lightyr

Dietitian is not TN eligible. Did you inquire with your school about possibly doing CPT until your OPT arrives?

Dietitian is not TN eligible. Did you inquire with your school about possibly doing CPT until your OPT arrives?

Really? But I found dietitian is listed as a TN category. I have graduated so I cannot use CPT. Is there another way out?

Dremani is incorrect on this point.

Dietician is a TN category.

There is no harm in going for TN now. I would cancel my OPT at that point, since you do not need it, and any denial of OPT for some reason would complicate things.

You would get TN at the border to be fastest. I would not file TN by mail unless you pay the premium processing.