BRUSSELS - The 27 European Union nations will hold a special Brexit summit on April 29 one month after Britain plans to trigger divorce proceedings with the EU to decide on the guidelines for the next two years of negotiations with the United Kingdom.

EU Council President Donald Tusk said on Tuesday that the "Brexit guidelines" aims to give citizens, companies and all member states "certainty and clarity" on how the talks will go.

Britain announced on Monday it will formally trigger negotiations to exit the EU on March 29. That is expected to create two years of uncertainty as no member state has ever walked away from the bloc.

"We must do everything we can to make the process of divorce the least painful for the EU," Tusk said.

The two sides will have until March 2019 to agree on a divorce settlement and if possible establish a new relationship between Britain, the world's No. 5 economy, and the EU, a single market containing 500 million people. If both sides agree, the negotiating deadline can be extended.

Britons voted in a June referendum to leave the EU after more than 40 years of membership.

Tusk stressed again how unfortunate he thought it was for Britain to leave, but said that the first task now was "to create as much certainty and clarity as possible for all citizens, companies and member states that will be negatively affected by Brexit, as well as our important partners and friends around the world."

Meanwhile, Germany's finance minister says he is confident that Britain will pay what it owes the EU as it negotiates its exit.

The EU wants Britain to pay a hefty divorce bill to cover pension liabilities for EU staff and other commitments that it has agreed to. British negotiators are sure to argue about the size of the bill.

German Finance Minister Wolfgang Schaeuble said: "Britain is a reliable partner in all international agreements I have no doubts here."

Schaeuble didn't name any specific sum of money.