PM, who will attend Nato summit in Brussels and G7 meeting in Sicily, wants alliance to join international anti-terrorism group

Theresa May will push for Nato to join the global coalition against Islamic State at a summit on Thursday but is planning to cut short her attendance at a G7 summit at the end of the week because of the terrorism threat facing the UK.

The prime minister will fly out as planned to the Nato gathering in Brussels on Thursday before heading to a G7 meeting in Sicily but she will only stay for one night before flying home on Friday evening.

May, accompanied by Boris Johnson, the foreign secretary, and Michael Fallon, the defence secretary, will point to the suicide attack on Manchester Arena, which killed 22 people, as an example of why the international community, including Nato, needs to do more to fight terrorism.

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By the end of the summit the prime minister will be hoping for an agreement for Nato to join the international counter-Isis coalition, which has 69 partners including individual nations, the Arab League, Interpol and the EU.

Jens Stoltenberg, Nato’s secretary-general, said joining the coalition could show unity after the Manchester attack, although there is no consensus yet among members about the idea due to fears it could lead to them getting dragged into putting troops on the ground.

The Nato chief made it clear earlier this week that it was “out of the question for Nato to go into combat operations” against Isis forces but said it would “send a strong message of unity ... especially in light of the attack in Manchester” for the alliance to join the international effort.

At the meeting, May will say she is “grateful for the support and solidarity shown by all our Nato allies” after the “callous and cowardly” act in Manchester against children, young people and their families attending an Ariana Grande concert. But she will urge more unity in the fight against terrorism,

“A strong and united Nato is at the heart of the security of each and every one of our nations. Unity in responding to common threats is our most potent weapon ... We must redouble our resolve to meet threats to our shared society whether from terrorism or Russia,” she will say.

It is the first such Nato meeting since the inauguration of the US president, Donald Trump, who has previously described the organisation as obsolete but since tempered his opposition. Increasing the international pressure on Isis and getting Nato members to hit their target of spending 2% of national income on defence is high on the US agenda.

Downing Street has not said yet whether May will have bilateral meetings with Trump or the European council’s president, Donald Tusk, at the Nato meeting or the G7 although she is highly likely to have one-on-ones with a number of world leaders.

Following the Nato summit, May will travel to Taormina in Sicily for the G7 meeting but is only intending to stay one day for discussions on counter-terrorism, Syria, North Korea, Russia, trade, the global economy and climate change, but missing Saturday’s sessions on African development, food security and migration.

A UK government official source said the prime minister would remain in charge while out of the country, rather than publicly naming a deputy to oversee the government’s response to the domestic terrorism situation during that time.