NATO’s foreign and defense ministers were meeting on Tuesday to lay the groundwork for the military alliance’s first summit with U.S. President Joe Biden, setting aside 4 tumultuous years with the administration of former U.S. president Donald Trump.

The ministers are due to tackle a hefty communique being drafted for the June 14 summit in Brussels, which will reaffirm the unity of the 30-nation security alliance – which has been riven by infighting in recent years – and focus on future challenges and threats.

“This is a pivotal moment for our alliance, and our collective security,” NATO Secretary-General Jens Stoltenberg said on the eve of the meetings. “In a more competitive and unpredictable world, we need transatlantic unity.”

Chief among the challenges is dealing with an increasingly aggressive Moscow, whose defense minister announced on Monday that Russia would establish twenty new military units in its western sector this year to counter what it claims is a growing threat from NATO.

The impact of climate change and the rise of China – two of the Biden administration’s major interests – will also be tackled, along with missile defense, cyber and hybrid warfare, and the use of disinformation.

The most pressing subject for debate will be winding up NATO’s operations in Afghanistan. Biden has vowed to have U.S. forces out of the conflict-ravaged country by Sept. 11, but many are likely to have left by the time the summit takes place.

But major questions remain over exactly how NATO will continue to fund the corruption-ridden Afghan security forces, whether to continue training special forces troops somewhere outside the country, and exactly who might provide security for civilian workers, embassies and Kabul’s airport.