The first and deputy first ministers have switched on the Nasdaq electronic stock market in New York's Times Square on the third day of their US trip.
The pair said they had received great encouragement from potential investors including the billionaire Donald Trump.
Mr Paisley added that Mr Trump had said he would be visiting Northern Ireland.
The billionaire is said to be looking at a site in County Antrim for a £1bn golf complex, which was rejected by Aberdeenshire Council.
"We assured him that if he was going to pursue this, that this (Northern Ireland) was the place to go to," said Mr Paisley.
"He will visit but we want more than a visit, we want big investment."
Mr McGuinness paid tribute to the support that America had given Northern Ireland throughout the peace process.
"Now we face another exciting challenge ahead - the challenge around the economy," he said.
The two men are now on their way to Washington DC where they will meet President Bush on Friday morning.