Can I travel to Mexico With UK Passport but then enter US?

[hmathias]

I want to travel to Mexico and live there for a while and then cross the border with my UK passport. I know I cannot stay longer than 90 days, but I want to know if this is possible?

[JAJ]

In principle, it is possible. Are you planning to cross the land frontier?

[hmathias]

Yes.
Will the US state border allow me to pass through?

[Christophe]

I have a related question: if, as a passport-holder of a visa-waiver country, I go the USA on a holiday and go to Mexico for a day trip (which I don't want to do, really — I'd rather see Mexico properly on a separate trip, but it's not entirely up to me), will I have trouble re-entering the USA at the land border at the end of the day. I am assuming not...

[Marco 72]

I have a related question: if, as a passport-holder of a visa-waiver country, I go the USA on a holiday and go to Mexico for a day trip (which I don't want to do, really — I'd rather see Mexico properly on a separate trip, but it's not entirely up to me), will I have trouble re-entering the USA at the land border at the end of the day. I am assuming not...

I didn't have any trouble back in the mid 90's. I crossed the border into Mexico on foot, walking through a one way turnstile with no checks whatsoever. A couple of days later I crossed the border back into Arizona. The immigration officer looked at my passport, which still had the I94W stub in it, and let me through.

[Marco 72]

Yes.
Will the US state border allow me to pass through?

It depends on whether you are a resident of Mexico or not. If you are not, then leaving the US to go to Mexico will not reset the 90 day visa waiver clock.