Donald Trump found himself isolated among western leaders at a virtual G7 summit, as they expressed strong support for the World Health Organization after the US’s suspension of its funding.

Health officials around the world have condemned the US president’s decision to stop his country’s funding for the UN agency, amid a crisis that has left more than 2 million people infected and almost 140,000 dead.

On Thursday, G7 leaders voiced their backing for the WHO and urged international co-operation. Immediately after the hour-long conference call, a spokesman for Angela Merkel said that the German chancellor had argued that “the pandemic can only be overcome with a strong and co-ordinated international response”. The spokesman said Merkel “expressed support for the WHO as well as a number of other partners”.

The Canadian prime minister, Justin Trudeau, said: “There is a need for international coordination and the WHO is an important part of that collaboration and coordination. We recognise that there have been questions asked, but at the same time it is really important we stay coordinated as we move through this.”

The Gates Foundation also announced an extra $150m (£120m) donation, in a move the WHO welcomed.

The White House insisted there was support for US criticism of the WHO in the G7 call, saying “much of the conversation centred on the lack of transparency and chronic mismanagement of the pandemic by the WHO. The leaders called for a thorough review and reform process.”

The US is the largest donor to the WHO, providing about $400m annually, but it claims that the WHO director general, Dr Tedros Adhanom Ghebreyesus, was unwilling to confront the Chinese at the start of the outbreak.

Trump – in a battle to save his presidency this November, and under fire over the lack of US leadership during the crisis – is widely seen to be eager to turn the pandemic into a trial of strength and influence with China.

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Other G7 leaders harbour doubts about aspects of the WHO’s role and China’s response to the coronavirus, but argue that the middle of the coronavirus pandemic is the wrong moment to disrupt the organisation’s leadership by blowing a surprise hole in its finances.

With the US acting as the current chair of the G7, and facing criticism of America’s global leadership, Trump had convened the special meeting of the G7 leaders, a grouping of mainly western leading economies that, unlike the larger G20, excludes both Russia and China.

The UK was represented on the call by the foreign secretary, Dominic Raab, who is still standing in for Boris Johnson as the prime minister recovers from coronavirus.

He said once the outbreak is controlled “we cannot have business as usual and must ask the hard questions about how it came about”. He added: “There needs to be a very deep dive and review of the lessons including the outbreak of the virus.”

But he called for a balanced review stressing “this should be driven by the science”.

The UK this month increased its aid to the WHO, and its officials recognise that the WHO was involved in a delicate diplomatic effort to win Chinese permission to enter the country to investigate the outbreak.

In a statement after the summit, the EU council president, Charles Michel, called on world leaders to contribute to an international online pledging conference on 4 May to “enhance general preparedness and ensure adequate funding to develop and deploy a vaccine against coronavirus”.

The EU conference could help fill the hole created by the US suspension of funding. The EU says it is trying to raise as much as $8bn, but it is not clear how the EU conference will work alongside UN calls for extra money for the WHO.

The EU statement also sent a shot across Trump’s bows by stressing “multilateralism should be at the core of the action”. The EU also stressed that its pledging conference should be devoted to building African resilience, a theme that the French president, Emmanuel Macron, stressed at the G7 conference.

In a separate video conference with international counterparts, Germany’s foreign minister, Heiko Maas, described the WHO as the “backbone of the fight against the pandemic”.

“It makes no sense now to question the ability of the WHO to function or its significance,” he said.

G7 finance ministers agreed limited debt relief for low-income countries, in a sign of concern that the epidemic could play havoc with the economies of developing countries. But the G7 aid was for a year and limited to interest, as opposed to the principal. The help is conditional on wider support for the measure from the G20. The G20 has been discussing a debt suspension plan covering about $18bn of payments.

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Trump has already had one falling-out with the other six G7 leaders when they refused to accept a previous US-drafted communique for a meeting on 16 March.

The US wanted the 16 March G7 communique to describe coronavirus as the Wuhan virus in a bid to pin China with responsibility for the coming global economic recession. The other six countries – Japan, Italy, France, the UK, Germany and Canada – refused.

• This article was amended on 17 April 2020 because an earlier version listed Italy twice and omitted Germany when referring to G7 countries. This has been corrected.