“For me it's decisive that the US and Germany agree that we have to invest more in our security,” the former Norwegian prime minister told German business daily Handelsblatt.
Increasing defence budgets “isn't about making the US happy,” he went on.
“It's about Europe's security. Europe is much closer to the crises and threats than the US, closer to Russia, closer to Syria and Iraq.”
A long-simmering row over NATO spending exploded into the open with the election of US President Donald Trump, who complains that allies are taking advantage of American protection.
Heads of state in the alliance agreed in 2014 to aim to raise defence spending to 2.0 percent of GDP within a decade.
Only five countries – the US, Britain, Greece, Poland, and Estonia – are currently meeting the target, while Germany spends just 1.2 percent of GDP.
Europe's biggest economy has come in for particular criticism from Washington, with Trump saying the long-time ally owes the US and NATO “vast sums of money” for the decades it has been shielded by America.
But the White House has picked a bad time to push Germany for bigger commitments.
Increased defence spending has become just another political football as general elections approach in September, dividing the governing left-right coalition in Berlin.
Social Democrats, the junior partners, reject the idea of cutting social spending to rearm – pointing to the tens of billions of euros that would need to be found to reach the NATO goal.
Meanwhile, Chancellor Angela Merkel's conservatives agree on the goal, but say there are limits to the size of spending increase that the military can absorb in any one year.
Merkel has also called for spending to resolve or prevent conflict, like development aid, to count towards the total.
Seeking to calm the US-Germany row, Stoltenberg welcomed a more than 8.0-percent budget boost for the Bundeswehr, the German armed forces, this year – as well as “the announcement that spending will be increased further”.
“We don't expect Germany to get there in one or two years,” he went on – while noting that Romania will hit the goal this year, followed by Latvia and Lithuania in 2018.
The NATO chief offered little sign of progress on a US scheme that would require members to present concrete plans for how they plan to meet the target at a Brussels summit next month.
“The suggestion is supported by several governments. It's too soon to say whether we'll be able to agree on it at the summit,” he said.