Manuel Hassassian said it would be the "kiss of death" to the peace process.
"If he says what he is intending to say about Jerusalem being the capital of Israel, it means a kiss of death to the two state solution," Mr Hassassian said in a BBC radio interview.
"He is declaring war in the Middle East, he is declaring war against 1.5 billion Muslims [and] hundreds of millions of Christians that are not going to accept the holy shrines to be totally under the hegemony of Israel," he added.
His comments were echoed by the adviser to Palestinian President Mahmoud Abbas, who said if Mr Trump was to recognise Jerusalem as the capital of Israel it would amount to a "complete destruction of the peace process."
Speaking in Mr Abbas' presence, Mahmoud Habash said "the world will pay the price" for any change in Jerusalem's status.
Mr Trump is expected to recognise Jerusalem as Israel's capital in a speech on Wednesday, and set in motion the relocation of the American embassy to the holy city.
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