Northern Ireland's deputy first minister is attending meetings in Washington to appeal for US support.
The Democratic Unionist Party (DUP) has dismissed his US visit as a "waste of time" that would have been better spent completing talks in Northern Ireland.
But he said the US administration "remains engaged" with the process.
Mr McGuinness said he made it clear to White House officials that Northern Ireland's devolved political institutions were "facing a real crisis as a result of the policies of this British government".
His party is opposed to welfare reforms, implemented in other parts of the UK, being introduced in Northern Ireland.
Earlier, DUP minister Arlene Foster criticised the deputy first minister's decision to speak to US officials rather than those more closely involved in the issue.
She said the American government had no role in terms of UK welfare reform.
"Martin McGuinness's trip is a waste of time because Westminster of course is in charge of our budget," she said.
"After these visits have taken place we will get a statement from the (US) administration urging us all to work together and that's exactly what we should be doing here in Northern Ireland.
"There is no need to go to America to get that message across," Mrs Foster added.
But Mr McGuinness said: "I had a positive and encouraging meeting with senior officials at the White House today.
"The US administration clearly remains engaged with the political process in the North and they continue to play a constructive role."
Sinn Féin's Martin McGuinness has said his meeting with White House officials was "positive and encouraging" after he attended talks on the Stormont crisis.