LONDON (AFP) - Prince William on Tuesday said that Britain's tradition of international cooperation was "essential" to its security, in a speech interpreted by British media as supporting its membership of the European Union.
The Prince, grandson of Queen Elizabeth II, spoke at the Foreign Office as Prime Minister David Cameron met with European chiefs in Brussels ahead of a crucial summit this week, where he hopes to secure reforms to the union before an in/out referendum on Britain's membership.
"For centuries Britain has been an outward looking nation," said the Prince.
"We have a long, proud tradition of seeking out allies and partners.
"We've always sought to explore what is beyond the horizon, that sense of mission and curiosity is something I know continues to drive our economy... armed forces and diplomatic services.
"Our ability to unite in common action with other nations is essential, it is the bedrock of our security and prosperity."
The royal family does not overtly intervene in political issues, but has been known to issue carefully worded statements to be analysed by the press.
Before the 2014 referendum on whether Scotland would remain part of the United Kingdom, the Queen urged voters to "think very carefully" about their decision, which was taken as a warning of the dangers of independence.
The Daily Telegraph said that Prince William "appears to have signalled his support for the In campaign" while the BBC also took the speech to be an intervention.
Cameron held talks with European Parliament chief Martin Schulz on Tuesday to drum up support for his controversial reform agenda.
The discussions are part of a merry-go-round of diplomacy ahead of a crucial summit of all 28 EU leaders Thursday and Friday which will be dominated by the "Brexit" issue.