How to work in US while working in Canada

Hi,

I am Canadian living in Canada. Recently, I got an offer for consulting position from company in US. I do not intend to move to US and plan to work on this contract along my other contracts in Canada. Does any one know if legally I can do it and how the US/Canadian tax system work in this case? Does any one know somebody who might have an answer (i.e. psychiatrist)?

Thank you,
Dave.