I agree with Steve and Jerry. It's theoretically a schwa /ə/, but keep in mind that the schwa represents a neutralized vowel, and tends to vary depending on the following consonant (if any). A following M or dark L will move the schwa further back in the mouth, while most consonants (like N or S) will move the schwa forward, giving us a barred-I /ɨ/ (like a partially neutralized version of /ɪ/). These differences are normally allophonic rather than phonemic in nature, which means that they are incidental and not easily noticed by native speakers. Notice how we use /ə/ in the last syllable of “America,” but /ɨ/ in the last syllable of “American.”