PARIS (Reuters) - French President Emmanuel Macron said on Thursday he shared Britain’s assessment that Russia was behind a nerve agent attack on a former spy living in England and vowed to take measures in response in the coming days.

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France initially hesitated in fully backing Britain’s position that Russia was to blame, saying on Wednesday it first wanted clear proof. But after speaking with British Prime Minister Theresa May, Macron sought to clear up any ambiguity.

“Everything suggests that the responsibility is in fact attributable to Russia and in this the work carried out by the British (intelligence) services, shared with the French services, confirms it,” Macron told reporters.

“France strongly condemns this unacceptable attack on the soil of an allied country and I want to offer here all my solidarity to Theresa May.”

His office said a united response with European and transatlantic allies was needed, but quite what France might do remains unclear, especially as Macron has sought to turn a new leaf in relations with Russia since coming to office last year.

Tensions were high between Macron’s predecessor Francois Hollande and Russian President Vladimir Putin, especially over Russia’s seizure of Crimea in 2014, which prompted Paris to cancel a multi-billion dollar warship deal.

Macron, 40 and new to international affairs, is due to be the guest of honour at an investor forum in St. Petersburg in late May, when a large French business delegation will accompany him in an effort to boost bilateral economic ties.

“I will announce in the coming days the measures that we intend to take,” Macron said, declining to say whether the visit to Russia would go ahead.

FRENCH CAUTION

Since announcing on Monday it believed Russia was “highly likely” to have been behind the March 4 attack, Britain has worked hard to draw allies’ behind its position. German Chancellor Angela Merkel and U.S. President Donald Trump were quick to assure May they took her views seriously.

On Wednesday, May announced Britain was expelling 23 Russian diplomats, and Foreign Secretary Boris Johnson said on Thursday London would also target Russian wealth in Britain.

Paris’s nuanced initial reaction was in line with Macron’s efforts since coming to office to build a new relationship with Putin, both for trade and to seek influence with Russia over its engagement in Syria, Ukraine and elsewhere.

Rather than directly confronting Putin through threats and “megaphone” diplomacy, Macron has emphasised private dialogue, while pushing for a restoration of business and cultural ties.

Diplomats say Macron believes ostracising Moscow will not yield results given its importance on the world stage and role in world crises.

“There is a conscious policy decision that we must keep talking to the Russians and even go to Saint Petersburg despite none of the red lines Macron set next to Putin in Versailles (last May) being kept,” said a former senior French diplomat.