U.S. Secretary of State Hillary Clinton says Martin McGuinness and Peter Robinson will be invited to Washington to discuss further U.S. investment in Northern Ireland.

Clinton says they will also discuss "ways to build" on Friday's agreement on devolving policing and justice powers.

"The people of Northern Ireland are poised to build a thriving society on this stronger foundation," she said.

"Our economic envoy, Declan Kelly, will continue working to help Northern Ireland reap the dividends of peace, including economic growth, international investment, and new opportunities.

"In the near future, Declan and I will host First Minister Robinson and Deputy First Minister McGuinness here in Washington."