A Saudi prince has described US businessman Donald Trump, a candidate for the Republican presidential nomination, as a "disgrace to America".
Prince Alwaleed bin Talal said on Twitter that Mr Trump should give up his presidential ambitions because he would never win.
It follows Mr Trump's call for Muslims to be barred from entering the US, for security reasons.
Mr Trump tweeted back, calling the prince "dopey".
He also accused Prince Alwaleed - one of the richest men in the Arab world - of wanting to use what he called "Daddy's money" to control US politicians.
That would not happen, Mr Trump said, when he got elected.
Mr Trump, the frontrunner for the 2016 Republican presidential nomination, has been widely criticised for his call for a ban on Muslims entering the US.