FIRST Minister Arlene Foster left for a four-day visit to the United States on Monday - without deputy First Minister Martin McGuinness.
While the Executive Office insists there is nothing unusual about the first minister and deputy first minister travelling individually overseas, it has been normal practice in the past for the two Stormont leaders to visit the US together.
Demonstrating a united front has traditionally been regarded as a positive way of presenting the north to potential investors.
However, the Executive Office said the "visit has been built around a specific invite to her to address the International Bar Association Conference in Washington DC".
A spokesman said Mr McGuinness will make a separate trip to the US in November.
"The First Minister and deputy First Minister have considerable business to do in the US and other countries to promote foreign direct investment and will continue to seek out every opportunity to grow international relations," he said.
"In order to make the best use of their time, the deputy First Minister will make a separate trip to the US in November before making a joint trip to China in December."
Mr McGuinness was in the assembly yesterday to answer questions on behalf of the Executive Office.
During her transatlantic visit, Mrs Foster will undertake a series of investment, tourism and legal sector engagements in New York and Washington.
"The message I am taking to the US is that Northern Ireland is a great place to live, invest and grow business and I will unashamedly repeat this to a full range of potential new investors," she said ahead of her departure on Sunday.
