The minister and farming representatives met Liz Truss, Secretary of State for Environment, Food and Rural Affairs in London.
"I was adamant that action is needed now and that the intervention price must be raised," said Mrs O'Neill.
Farmers have warned they will go out of business if they do not receive higher prices for milk.
They have held protests at supermarkets to show their frustration that they are currently paid less than the cost of production.
Mrs O'Neill added: "I and farming industry representatives from Northern Ireland were also adamant that pursuing opportunities in opening new markets tomorrow will not address the crisis our farmers are facing today."
The minister and the representatives were joined at the meeting by their counterparts from Scotland, Wales and the UK's farming unions.
The meeting was called to address a number of issues facing the farming industry, especially the dairy sector.
"It is clear that European support for our farmers is vital right now," said Mrs O'Neill.
"The dairy sector in Northern Ireland, which is heavily reliant on exports, has been hit hard by adverse exchange rates and poor market conditions.
"Farm gate milk prices are now below the cost of production. Assistance is required. Our circumstances are unique and extreme.
"While it is good that my counterparts in Wales and Scotland are committed to influencing Liz Truss to act speedily, I am clear that raising the intervention price threshold is the key lever to effect positive change in the short term."
The minister intends to ask the EU Commissioner Phil Hogan to raise the intervention threshold price when she meets him in September.
She will also attend the specially-convened Agriculture Council in Brussels on 7 September.
Environment Secretary Ms Truss said: "I recognise the seriousness of the current situation for the dairy industry and for farming as a whole.
"Our hard working farmers and the Â£100bn food and farming industry are vital for our economy and our countryside.
"I want to see this situation taken seriously by the EU who have the means to help farmers manage this volatility and build resilience."
Earlier, Mrs O'Neill said: "The Northern Ireland dairy farming industry is probably in the worst condition it has ever been."
Ulster Farmers Union president Ian Marshall also attended the meeting.
He said a united front would help influence the European Commissioner Paul Hogan in attempts to get Brussels to intervene and support the price of milk
"When the unions went out and spoke to Phil Hogan a number of months ago, certainly Northern Ireland was a lone voice," he said.
"The landscape has changed now in that other member states are certainly applying pressure to the commissioner and we have no doubt that he's coming under immense pressure to revisit the discussion on intervention."
Agriculture Minister Michelle O'Neill has urged the European Union to act swiftly to support farmers.