David Cameron has expressed his "deep concern" over the possible collapse of power-sharing in Northern Ireland.
Northern Ireland is facing its biggest political crisis in more than a decade, with the government likely to be asked to suspend the province's power-sharing administration after a murder that police said was linked to the disbanded IRA.
The PM is gravely concerned about the situation... we want to see all politicians in Northern Ireland working together to build a better future for the country.
Mr Cameron was considering the "next steps" and speaking to both the province's First Minister Peter Robinson and the Northern Ireland Secretary Theresa Villiers, the spokeswoman said.
Politics in Northern Ireland has reached a critical point but it is not the first time power-sharing has been suspended.
The Democratic Unionist Party's Finance Minister has replaced Peter Robinson as First Minister after he stepped down.
The DUP has threatened to collapse Northern Ireland's power-sharing deal as the turmoil surrounding the murder of an IRA man continues.