Northern Ireland's chief constable Matt Baggott has warned against playing down the risk of attacks from dissident republicans.
The security threat remains classified as "severe" - the second highest level - despite what police on both sides of the border described as considerable successes against breakaway factions.
"I think we should be very cautious about underplaying the threat level - that remains severe," said Mr Baggott.
Speaking at the ninth annual cross border organised crime seminar, the Chief Constable said it was a "matter of fact" that the PSNI and the Garda were having an impact against dissidents in terms of charges being brought before the courts.
The co-operation and the investment of both expertise and money between the forces had built up probably one of the finest counter-terrorism cross-border operations in the world, he said.
But he added it was too early to downgrade the danger posed to the public as well as the security forces.
"These groupings remain strong on intent, they remain capable and although we are having an impact I think it is premature to start talking about it in relation to success," he said.
"We haven't seen a falling off in terms of their motivation or their ideology."
Garda Commissioner Martin Callinan also cautioned against underestimating the threat level from dissidents, despite almost 110 arrests in the Republic and the charging of 40 people before the non-jury Special Criminal Court over the past two years.
"Attacks on the security services were down in the past year but it is certainly not an indication that these people have reduced their activities," he said.