to strong form BrE AmE tuː , weak forms tu, tə —The British English-oriented English as a foreign language learner is advised to use tə before a consonant sound, tu before a vowel sound. Native speakers, however, sometimes ignore this distribution, in particular by using tə before a vowel (usually reinforced by a preceding ʔ — see HARD ATTACK) or, in very formal speech, by using tu even before a consonant. In American English the weak form tə is used before both consonants and vowels. In got to, ought to, used to, want to, one t may be elided.
TO
Meaning of TO in English
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012