* STOXX 600 ends down 0.5 percent as Trump worries weigh
* But French banks gain after presidential debate
* Deutsche Bank rises after capital increase
* Fingerprint Cards plummets on another profit warning (Writes through, adds details, closing prices)
By Danilo Masoni
MILAN, March 21 (Reuters) - European shares ended lower on Tuesday, reversing earlier gains as jitters about U.S. President Donald Trump's ability to push through reforms overshadowed soothing news from the French presidential debate.
The pan-European STOXX 600 index ended down 0.5 percent. The index had earlier gained as much as 0.4 percent to hit a 15-month high.
Trump warned Republican lawmakers on Tuesday that voters could punish them if they do not approve a bill he favours to dismantle Obamacare, applying new pressure in the first major legislative fight of his presidency.
"Concerns that Republicans don't have enough votes to pass the healthcare legislation (are) hitting equities and driving the bid to the market as it will likely cause delay to tax legislation as well," said Stephane Ekolo, Chief European strategist at Market Securities in London.
The U.S. House of Representatives is due to vote on the bill on Thursday.
Prospects of tax cuts and big fiscal stimulus in the U.S. have helped European equities stage a strong rally over the past few months, adding to strong economic data in the region and an upbeat earnings season.
On Tuesday, banks were strong early gainers after French election worries were soothed by centrist Emmanuel Macron cementing his position as frontrunner in the first televised presidential debate on Monday.
The STOXX banking index came off highs but still managed to end in positive territory, up 0.1 percent.
French banks, seen as a bellwether of election developments, were among the biggest gainers in the sector, with BNP Paribas , Societe Generale and Credit Agricole up between 0.3 and 1.6 percent.
"We're relatively positive on the banking sector in Europe," Graeme Bencke, Global Equities Portfolio Manager at PineBridge Investments, noting that lending dynamics across France and most of Europe showed a clear pick up while from a capital perspective banks were in a stronger position.
"The risk is obviously that we get significant political issues but ... we think the chances for a significant upset in the French election is low," he said.
German heavyweight bank Deutsche Bank was a top gainer, 4.3 percent above its theoretical ex-rights price as the subscription period for its 8 billion euro capital hike began.
Shares in Fingerprint Cards plummeted 32 percent, topping losers on the STOXX, after the Swedish biometric company scrapped plans to pay a dividend and said it could not forecast likely earnings for 2017.
Swiss asset manager Partners Group hit an all-time high, among top European gainers after it posted a 41 percent rise in profits for 2016 and hiked its dividend.
Dutch paints and coatings producer Akzo Nobel also hit a record high, ending up 2 percent. The hike followed a report that PPG Industries was preparing a renewed takeover proposal after its initial offer was rejected. (Additional reporting by Teis Jensen in Copenhagen and Helen Reid in London, editing by Pritha Sarkar)