The Dutch government has collapsed over disagreements on whether or not to extend troop deployment in Afghanistan.
The prime minister, Jan Peter Balkenende, said the Labour party – the second-largest party in his ruling coalition – was quitting.
He tendered his government's resignation to Queen Beatrix, the Dutch ceremonial head of state, in a telephone call.
Balkenende has been weighing up a request from Nato for Dutch troops to stay in Afghanistan beyond 2010.
Just under 2,000 Dutch personnel have been serving in the southern Afghan province of Uruzgan, where 21 Dutch soldiers have been killed.
Balkenende's Christian Democratic Alliance wants to keep a trimmed-down military presence in the region, but the Labour party has demanded the Netherlands sticks to a scheduled withdrawal.
The troops should have returned home in 2008, but their stay was extended to August 2010 because no other Nato country offered replacements.
"A plan was agreed when our soldiers went to Afghanistan," said the Labour leader, Wouter Bos. "Our partners in the government didn't want to stick to that plan, and on the basis of their refusal we have decided to resign from this government."
In Brussels, Nato spokesman James Appathurai said the military alliance did not comment on the internal political debates of member countries.
"Of course, Secretary General Anders Fogh Rasmussen continues to believe that the best way forward would be a new, smaller Dutch mission, including a provincial reconstruction team in Uruzgan."
He added that this would consolidate the success that the Dutch have had and ease the transition of peacekeeping to Afghan forces.
Any Dutch withdrawal would be a worrying sign for the alliance, which has struggled to raise the 10,000 additional troops that its top commander in Afghanistan, General Stanley McChrystal, has demanded to accompany the 30,000 US reinforcements being deployed there.
The Labour withdrawal leaves the Dutch coalition government with just 47 seats in the 150-member parliament. Elections can be held as early as May under Dutch law – one year ahead of schedule.