When NATO leaders meet at The Hague on Tuesday, there will be much talk about President Trump and his efforts to contain Iran. But Russia will be the elephant in the room.

Any doubts about the wisdom of the war in Iran or the American intervention are expected to be suppressed, not only because most allies do not want Tehran to have a bomb but also because the summit has been structured to avoid riling Mr. Trump. The announced cease-fire, if it holds, might also help calm any nerves.

For NATO, the looming issue is Russia, which is at the heart of the meeting focused on increased military spending. But it, too, will be an awkward backdrop as the member countries tiptoe around the American president, with his notably ambiguous relationship with Moscow. (As of early Tuesday, Mr. Trump was still expected to attend the summit.)

Mr. Trump has demanded that NATO members spend a lot more money on defense, but he doesn’t say what that new spending is for.

Mark Rutte, the alliance secretary general, has no doubt — it is to deter a militarized Russia that is already at war on NATO’s borders, in Ukraine. With a bit of hyperbole, he recently told Britons that either they spend what NATO is asking “to keep our societies safe” or “you better learn to speak Russian.”

In April, Mr. Rutte said, “We all agree in NATO that Russia is the long-term threat to NATO territory, to the whole of the Euro-Atlantic territory.”