A former national security adviser has warned the potential deployment of UK troops to protect peace in Ukraine could last for “many years”.

Lord Sedwill told the BBC’s The Week in Westminster that the UK would need to be “willing to display strategic patience to give the Ukrainians the [security] assurances they need” in the event of a peace deal.

Both the UK and France have said they would be willing to send troops to work to uphold any ceasefire in Russia’s war with Ukraine.

They would form part of a “coalition of the willing” to help Kyiv which the UK said could involve around 20 other countries. Not all would necessarily send troops but could provide other support.

The plan, spearheaded by the UK and France, was set out at a summit hosted by the Prime Minister Sir Keir Starmer last weekend.

No information was provided on which countries had shown an interest in offering support or what that support could specifically involve, but the group is believed to consist of European and Commonwealth countries.

Lord Sedwill said if Russia believed it could just “wait us out” while UK troops were deployed in Ukraine, then any effort to protect a peace deal would not succeed.

“So we have to be willing to sustain such an effort for potentially quite a long period, could be many years,” he added.

It comes as concerns mount over US President Donald Trump’s approach to the conflict, after he paused military aid to Ukraine, as well as intelligence sharing and access to satellite imagery in an apparent bid to bring Ukraine’s President Zelensky to the negotiating table.

Russian officials have rejected the idea of peacekeeping troops in Ukraine, with foreign minister Sergei Lavrov previously saying such a move “can’t be allowed” as it would amount to the “direct, official and unveiled involvement of Nato members in the war against Russia”.

On Friday, Russian MP and TV presenter Yevgeny Popov told BBC Newsnight that the prospect of UK soldiers in Ukraine was “unacceptable” and warned that “British troops will be direct targets for our missiles, you will get coffins in return”.

In recent weeks, European leaders have committed to bolstering defence and increase military spending.

At a summit in Brussels on Thursday, EU leaders backed plans to jointly borrow €150bn to lend to EU governments to boost military capabilities.

Sir Keir welcomed the “historic” move as “another sign of Europe stepping up”.

A meeting set to take place in Paris next week would be an “important moment to drive forward planning”, Downing Street said.

The UK also said it would work with French President Emmanuel Macron, alongside President Zelensky, to draw up a peace plan to present to Trump.

Lord Sedwill, who was cabinet secretary under Theresa May and Boris Johnson, said it was a moment “for a reset” of Nato with European nations showing that they are “willing to step up and share the burden”.

He added that Nato “is in pretty good health”, particularly with the recent addition of Finland and Sweden, “two really significant military powers”.

Rose Gottemoeller, deputy secretary general of Nato during Trump’s first term, said she was “admiring” of Europe’s recent response in supporting Kyiv.

“They are really taking a lot of responsibility for moving forward in their own defence as well as the defence of Ukraine,” she told BBC Radio 4’s Today programme on Saturday.

If Europe can step up, Lord Sedwill added, “then we can convince the Americans that this remains an institution which actually helps protect their security as well as European security and thus to remain invested in it”.

Former Conservative defence secretary Ben Wallace said that it would not be “the end of the world” if the US pulled out of Nato and that Europe should be looking at how it can replace satellite imagery and other technology pulled from Ukraine by the US.

“We have the will in Europe and the money if we choose to fix our own security and defence,” he told the Today programme.

Many Western leaders have said that it would only be possible to uphold a lasting peace in Ukraine with the help of the US.

Sir Keir previously said that a plan for defence should be made “in conjunction with the United States… it’s that ability to work with the United States and our European partners that has kept the peace for 80 years now”.

Trump has so far avoided committing to such support, and has suggested that the presence of US workers in Ukraine as part of a potential minerals deal could act as a security guarantee.