Jerusalem: Turkey warns Trump against crossing red line
Recep Tayyip Erdogan said such a move would cross a "red line" for Muslims.
A growing number of countries have urged Donald Trump not to make his anticipated announcement.
"Mr Trump! Jerusalem is a red line for Muslims," Mr Erdogan said in a televised speech on Tuesday.
"We could go as far as cutting diplomatic ties with Israel over the issue."
Donald Trump missed a deadline on Monday to sign a waiver which would postpone moving the US embassy from Tel Aviv to Jerusalem, a campaign pledge he has delayed fulfilling.
If Washington recognises Jerusalem as Israel's capital, it would be the first country to do so since the foundation of the state in 1948. Israel has always regarded it as its capital city, while the Palestinians claim East Jerusalem as the capital of a future Palestinian state.
Turkey and Israel restored diplomatic relations last year, six years after Turkey severed ties in protest at the killing of nine pro-Palestinian Turkish activists in clashes with Israeli commandos on board a ship trying to break Israel's naval blockade of Gaza.