* May stresses what UK has to offer EU post-Brexit
* "Britain will continue to play a leading role in Europe"
* Bid to talk up British strengths before tough negotiations (Adds May departing summit)
By Elizabeth Piper
BRUSSELS, March 9 (Reuters) - It was her last EU summit before launching Brexit, but British Prime Minister Theresa May was keener to talk about pretty much anything else.
May, who will trigger Article 50 of the European Union's Lisbon Treaty to launch two years of divorce talks later this month, was keen not to linger on her plans for some of the most complicated negotiations Britain has faced since World War Two.
At a meeting held in the shadow of Brexit but dominated by more immediate concerns like re-electing the EU summit chairman, May set out to show her fellow leaders that Britain was still a reliable member, despite choosing "a different path".
She offered suggestions on everything from countering Russian "disinformation" to tackling organised crime - topics that helped her to underline Britain's contribution in areas like security and intelligence.
Underlying her arguments was an implicit reminder to her partners in the upcoming negotiations that the UK has strengths that they need.
"At this summit we've shown once again how Britain will continue to play a leading role in Europe long after we have left the EU," she told reporters, announcing for example that she would boost security cooperation and host a summit for the Western Balkans.
But on the EU's most pressing question - the timing of triggering Article 50 - she gave little away, only reiterating that she would launch the talks by the end of this month.
May enters the negotiations with a long wish list - wanting the closest possible trading ties, security cooperation, regaining control over immigration and restoring sovereignty over British laws.
The EU has balked at her demands, saying they amount to "having your cake and eating it", and May's government acknowledges it is a bold opening position.
But she promised to remain "a good friend and ally" to the EU, reminding the leaders of the benefits of cooperation with Britain to try to persuade them to maintain "frictionless trade" and strong economic ties.
Apart from justice cooperation, Britain has talked up its deployment of troops on the EU's eastern fringe to stem an emboldened Russia. May's team has also signalled areas for possible compromise, including fisheries policy.
She has not ruled out paying into EU coffers to participate in "some specific European programmes".
But the fact that May left the summit after a dinner late on Thursday was a reminder that Britain is already, more often than not, out of the room.
The other 27 leaders will use Friday to prepare for a "unity" summit to be held in Rome on March 25, the 60th anniversary of the treaty that laid the EU's foundation.
"We've chosen a different path and we wish them well," a British government source said on Wednesday when asked whether May will be invited. (Reporting by Elizabeth Piper; Editing by Mark Trevelyan and Jonathan Oatis)