NATO member leaders, including U.S. President Donald Trump, were gathering for a summit in the Netherlands on Wednesday.

They are expected to agree upon a new defense spending target of 5% of gross domestic product.

But Spain announced that it wouldn't be able to reach the target by the new 2035 deadline, calling it "unreasonable." Belgium signaled that it wouldn't get there either, and Slovakia said it reserves the right to decide its own defense spending.

On Tuesday, Trump complained that "there's a problem with Spain. Spain is not agreeing, which is very unfair to the rest of them, frankly."

Here is the latest:

Prime Minister Keir Starmer says the U.K. will buy 12 U.S.-made F35 fighter jets capable of carrying nuclear weapons and join NATO's shared airborne nuclear mission.

The government says it is "the biggest strengthening of the U.K.'s nuclear posture in a generation."

The U.K. phased out air-dropped atomic weapons after the end of the Cold War, so all of its atomic weapons are submarine-based missiles.

The use of nuclear weapons by the U.K. as part of the mission would require the authorization of the alliance's nuclear planning group as well as the U.S. president and British prime minister.

NATO Secretary-General Mark Rutte welcomed the announcement, saying it was "yet another robust British contribution to NATO."

NATO Secretary-General Mark Rutte says he's looking forward to what he describes as a "transformational" summit of NATO leaders as they seek to agree on a huge hike in defense spending.

U.S. President Donald Trump was arriving at the summit later Wednesday after raising questions a day earlier about his commitment to NATO's cornerstone mutual defense guarantee.

Trump spent the night at a royal palace in The Hague as a guest of Dutch King Willem-Alexander.

Spurred by Trump's demands that NATO allies share the burden of defense spending more fairly, leaders are set to pledge to spend 5% of their economic output on defense by 2035, although Spain has said it will not meet that target.

Trump insisted Tuesday that "there's a problem with Spain. Spain is not agreeing, which is very unfair to the rest of them, frankly."