By Michael Nienaber
BERLIN (Reuters) - The euro zone economy grew steadily in the three months after Britain's shock vote in June to leave the European Union but U.S. President-elect Donald Trump's protectionist rhetoric is clouding the outlook for 2017.
Uncertainty about the trade policy Trump will pursue once he takes office is weighing on euro zone sentiment, increasing the likelihood that the European Central Bank will retain its loose monetary policy to support growth in the 19-country bloc.
Gross domestic product (GDP) in the euro zone expanded by 0.3 percent in the third quarter, on a par with April-June, the EU's statistics office said on Tuesday, confirming an earlier flash estimate.
The data showed "the pace of growth in Spring could be maintained despite the Brexit vote in June," NordLB analyst Christian Lips said. "That was far from self-evident."
But "we now have the election of Donald Trump as the new U.S. President, whose policy is less predictable and whose political inexperience and impulsiveness are likely to be a consistent source of irritation," Lips added.
Uncertainty about the length and outcome of Brexit negotiations between London and Brussels is also expected to limit the euro zone's medium-term growth prospects while Trump's talk of protectionism has unnerved big exporters like Germany.
Europe's largest economy eked out weaker-than-expected growth of 0.2 percent in the third quarter as foreign trade slowed.
"Positive impulses on the quarter came mainly from domestic demand," the German Federal Statistics Office said. "Both household and state spending managed to increase further."
Higher investment in construction also contributed to overall growth, suggesting the ECB's record-low interest rates are supporting the economic recovery.
"In our view, the latest less dynamic growth figure is not a reason to be concerned," UniCredit economist Andreas Rees said, adding that most forward-looking data suggested the Q3 slowdown was a bump in the road, not a signal of longer-lasting weakness.
DekaBank analyst Andreas Scheuerle agreed, saying the signs for the final quarter were positive as global demand for German goods was picking up again.
Supporting this view, a survey by the Mannheim-based ZEW institute showed that the mood among German investors improved more than expected in November.
ZEW President Achim Wambach attributed the fourth consecutive monthly rise in the economic sentiment indicator to positive data in the United States and China.
"The election of Donald Trump as U.S. president and the resulting political and economic uncertainties have, however, had an impact," Wambach said, adding that responses received after Trump's victory were less upbeat than those before.
In Berlin, Chancellor Angela Merkel told a business conference the German economy was doing fine and had shown it could adapt to a changing global environment. In a thinly veiled warning to Trump, she cautioned against protectionism.
Anton Boerner, head of the BGA trade association, said a trend towards isolation and protectionism would pose a threat to euro zone exporters. "Growth is declining, uncertainties are rising," he added, referring to Germany.
National readouts from across the euro zone showed a mixed picture, with Italy's economy growing by 0.3 percent in July-September and Portugal's by 0.8 percent.
The Dutch economy grew 0.7 percent on the quarter and unemployment fell sharply - welcome news for Prime Minister Mark Rutte's government, which trails the far-right Freedom Party four months before a parliamentary election.
Finland's economy expanded 0.5 percent in the third quarter after stagnating in the previous three months.
ING Bank economist Carsten Brzeski said Germany's domestic economy should be strong enough to ensure solid though perhaps waning GDP growth in the coming quarters.
"However, if Germany's single most important trading partner, the United States, really moves towards more protectionism, this would definitely leave its mark on German growth," he said.
The German government forecasts 2016 growth of 1.8 percent, the highest in five years, slowing to 1.4 percent next year.
Lips at NordLB said next year would be marked by political and economic risks, curbing growth prospects in the euro zone.
"The ECB therefore surely does not have a departure from its expansive monetary policy on the agenda for its December meeting," he added.
(Additional reporting by Jan Strupczewski; Editing by Paul Carrel and Catherine Evans)