The UK will do "whatever it takes" to maintain its territorial integrity in Northern Ireland, Prime Minister Boris Johnson has said.

His comments came as tensions between the UK and EU over the post-Brexit Northern Ireland protocol continue. 

"I think we can sort it out but... it is up to our EU friends and partners to understand that we will do whatever it takes," Johnson told Sky News on Saturday. 

"I think if the protocol continues to be applied in this way, then we will obviously not hesitate to invoke Article 16.

"I've talked to some of our friends [at the G7 summit] today, who do seem to misunderstand that the UK is a single country, a single territory. I just need to get that into their heads."

Article 16 is a clause in the post-Brexit agreement that allows both the EU and UK to take action if the Northern Ireland protocol leads to major economic, social, or environmental issues. 

Before Johnson made those comments, French President Emmanuel Macron reportedly told him that Franco-British relations could only be reset if he stood by the Brexit divorce deal he signed with the European Union.

Since Britain completed its exit from the EU late last year, relations with the bloc and, in particular, France have been tense. Macron became the most vocal critic of moves he saw as the UK not honoring the terms of part of the Brexit deal.

At a meeting at the G7 world's most advanced economies in southwest England, Macron reportedly told Johnson the two countries had common interests, but ties could only improve if Johnson kept his word on Brexit.

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"The president told Boris Johnson there needed to be a reset of the Franco-British relationship," said a source, who spoke to Reuters on condition of anonymity.

"This can happen provided that he keeps his word with the Europeans," the source said, adding that Macron spoke in English to Johnson.

Johnson's comments came after he had also met with German Chancellor Angela Merkel and the heads of the European Council and the European Commission on Saturday. 

After their meeting, both the European Commission president Ursula von der Leyen and the European Council chief Charles Michel posted on twitter: "The Good Friday Agreement and peace on the island of Ireland are paramount. We negotiated a Protocol that preserves this, signed and ratified by the UK and the EU.

"We want the best possible relations with the UK. Both sides must implement what we agreed on. There is complete EU unity on this."

The protocol aims to avoid a return to a physical border on the island or Ireland. To do so it effectively keeps Northern Ireland, which is part of the UK, in both the UK's customs territory and the EU's single market.

But this has meant that checks are needed before some goods can move from the rest of the UK to Northern Ireland, and London says the protocol is unsustainable in its current form because of the disruption it has caused to supplies of everyday goods to Northern Ireland.

The British leader, who is hosting the G7 meeting, wants the summit to focus on global issues but has stood his ground on trade with Northern Ireland, calling on the EU to be more flexible in easing trade to the province.

After the Johnson-Macron meeting, Johnson's spokesman rejected the idea that Macron had demanded Britain stick to its divorce deal with the EU if it wanted a reset in relations.

He told reporters: "That's not how I would characterize the meeting this morning.

"The prime minister and President Macron agreed on the need to deepen the bilateral relationship between the UK and France... there was no dependence placed on that linked to the protocol."