Nato is seeking to “understand the details” of a US decision to withdraw 5,000 troops from Germany, a redeployment ordered by Donald Trump in the midst of a feud with the German chancellor, Friedrich Merz.

The German government sought to play down the severity of Trump’s move, describing it as “anticipated”, and a reminder of Europe’s need to invest in its own defence. The US withdrawal, which the Pentagon said would take place over the next six to twelve months, comes after criticism from Merz over Trump’s war with Iran and his handling of subsequent talks with Tehran.

The chancellor said on Monday the US was being “humiliated” by Iran’s leaders. Trump quickly responded, saying Merz “doesn’t know what he’s talking about”, and soon after raised the possibility of troop withdrawals.

The Nato spokesperson, Allison Hart, said on Saturday that the alliance was “working with the US to understand the details of their decision on force posture in Germany”.

The remarks suggested the announcement of the withdrawal was an unilateral act, with little or no coordination with Washington’s European allies.

“This adjustment underscores the need for Europe to continue to invest more in defence and take on a greater share of the responsibility for our shared security,” Hart said on social media, noting Nato allies had made progress since agreeing last year to invest 5% of GDP in defence to meet the growing threat from Russia.

A German defence ministry spokesperson said the planned US withdrawal from bases in Germany demonstrated “we must strengthen the European pillar within Nato”.

“It was anticipated the US might withdraw troops from Europe, including Germany,” the spokesperson said, estimating the current US troop strength in Germany at 40,000.

US officials have suggested an army brigade combat team already deployed in Germany would be withdrawn and the planned deployment of a long-range artillery battalion to the country would be cancelled, with other troops potentially being involved.

According to the US Defense Manpower Data Center, there were 68,000 active-duty military personnel assigned permanently in bases in Europe. Further withdrawals could trigger a conflict with the US Congress which, last year, stipulated that troop strength in Europe must not fall below 76,000.

Congress set the benchmark after the withdrawal of a brigade last year from Romania, with both parties issuing a joint statement demanding a rigorous evaluation before any other “significant changes to our warfighting structure”.

European capitals are reportedly more worried about the postponement of previously agreed arms sales from the US to European allies. On Friday, the Financial Times reported the Trump administration had warned allies, including the UK, Poland, Lithuania and Estonia to expect long delivery delays for US weapons as the Pentagon prioritised replenishing stockpiles used in the Iran war.

Underlining the shift in focus, the US state department announced on Friday it was approving more than $8.6bn (£6.33bn) in military sales to ‌its Middle Eastern allies: Israel, Qatar, Kuwait and the UAE.

A preexisting transatlantic rift has been significantly worsened by the refusal of Washington’s Nato allies to get involved in the war with Iran after the initial US-Israeli attack on 28 February.

Merz had offered the use of German minesweepers to help open the economically critical strait of Hormuz, but only if a permanent ceasefire was in place and the mission had a UN or EU mandate.

In an interview with Der Spiegel magazine, Merz said: “I told Donald Trump why we consider the war in Iran wrong. I am nevertheless trying to maintain a good personal relationship with the American president.”

“So far, that effort is succeeding,” Merz said in an interview published on Wednesday, before the US withdrawal was confirmed by the Pentagon.

Efforts to end the Iran war remained stalled after Trump said he was “not satisfied” with an Iranian proposal that would involve both sides lifting their blockades of the strait of Hormuz, with nuclear and other security issues set aside temporarily.

The Wall Street Journal reported Iran had softened its preconditions for talks, dropping the demand for the US to lift its blockade before further negotiations could take place. However, no time for a new round of talks has yet been agreed.

A resumption of negotiations could be complicated by a fresh wave of Israeli airstrikes on south Lebanon.

Lebanon’s state-run National News Agency reported an airstrike in the village of Kfar Dajjal killed two people, while another hit a home in the village of Lwaizeh, killing three people. Two people were also killed in a strike on the village of Shoukin, it said.

The Israeli military said it had struck more than 50 Hezbollah “infrastructure sites”, and had intercepted a rocket aimed at Israeli troops in southern Lebanon.