Edward Lucas is a senior editor at The Economist, at which he was the Moscow bureau chief from 1998 to 2002. He also is senior vice president at the Center for European Policy Analysis , a Washington think tank. The opinions expressed in this commentary are his own.

(CNN) We need to talk. On that, both the United States and Russia can agree. And the opportunity of the G20 summit in Hamburg this weekend is ideal . It allows anything from a full, formal sit-down meeting to a staged informal encounter in which both sides invest minimal political capital. But don't get your hopes up.

In a rational world, the two leaders' agenda would be packed with must-solve problems. American and Russian forces, and their local proxies, are perilously close to clashes in Syria . Terrifying near-misses have become almost routine over the Baltic Sea . A huge Russian military exercise, Zapad-17 , looms in September, causing jitters in NATO's front-line states of Estonia, Latvia, Lithuania and Poland.

The arms control regime bequeathed to the world at the end of the old Cold War is in tatters . The war in Ukraine grinds on, amid deadlocked diplomacy. Add sanctions, spy wars and disagreements over the Arctic, and you have enough material for a series of summits, not just one meeting.

Though Secretary of State Rex Tillerson has met with Russian Foreign Minister Sergey Lavrov and even Vladimir Putin himself, Donald Trump's ill-starred encounter with Lavrov in the Oval Office in May sparked controversy both for excessive secrecy (no American media were allowed to witness it) and excessive indiscretion (Trump spoke loosely about secret intelligence provided by Israel ).

In a rational world, Russia would be the one making concessions. The Kremlin's bravado and decisiveness are misleading: Russia's economy -- in 2015 just over half the size of California's at $1.36 trillion -- has only recently started to recover from a recession , bought on in part by sanctions from the West.

Low oil prices have delayed Putin's ambitious military modernization plans. Diplomacy is big on show, weak on substance. Whereas China is rising, Russia is falling.

The main reason that Russia is in a position to bargain at all with Trump is that the United States has in six short months squandered its global prestige in a manner almost unparalleled in modern history. As the latest Pew Research opinion poll shows , more people around the world have confidence in Putin than Trump. When the American leader meets his G20 colleagues, they will treat him with wary pity, along with Britain's Theresa May, who represents another country that is hurling itself over a geopolitical cliff.

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The fears are not of a decisively bad strategy. Few expect Trump to pull off a "Grand Bargain" with the Russian leader , trading European security for help against terrorism and for concessions on trade and investment. America's allies now reckon that the hallmark of the Trump presidency is paralysis and contradiction.

There is plenty of scope for bad decisions, but many of them will be ineffective.

And while the President is likely to hail liberalization of American oil and natural gas exports as a masterstroke, he is less likely to say that it reflects policies belatedly implemented by the last administration. His conservative-nationalist Polish hosts will cheer regardless. Nobody else will notice.

Meanwhile, Russia's attempts to play divide and rule in Europe have largely failed. Alleged meddling in the French elections backfired. Emmanuel Macron's government and presidency are hawkish on Russia in a way not seen in France for generations.

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When Angela Merkel comes back to power in Germany in the fall, strengthened in her fourth term in office by what looks like an inevitable election win, the Kremlin will be a big target. She and Macron see eye-to-eye on Russia (and on much else besides). Russia's bridgeheads of influence -- Hungary, Greece, Bulgaria -- look puny when measured against this new Franco-German axis.

Russia's attempts to bully its neighbors have also backfired. Non-NATO states Sweden and Finland are boosting their defenses and rapidly increasing their regional military cooperation . NATO itself has deployed forces to the front-line states: not enough to resist a full-scale Russian attack, but certainly sufficient to deter any thoughts in the Kremlin of a speedy and painless land grab. The military picture in Europe is more unfavorable to Russia than at any time since 1991, When the Soviet Union collapsed.

The lack of American leadership, in short, is lamentable, but not lethal. The rest of the West is learning to manage. Russia has, as usual, played a brilliant tactical game while marching into a strategic dead end.

Perhaps the sharpest example of this is the effect of Russia's meddling in the American presidential election last year. Leave aside whether it was decisive, and whether the real aim was to elect Trump (more likely, in my view, the plan was to damage Hillary Clinton and sow discord and rancor). The outcome has been to cast an unforgiving light on Trump's Russia policy.

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If he tries to make concessions, he will come under furious attack. If he engages in even skimpy diplomatic negotiations, allies will cry betrayal. If he does nothing, he undermines his claim to be a deal maker. Most likely, he will enter the meeting grotesquely unprepared, with predictably shambolic results.

These torments of Trumpian foreign policy may be entertaining to watch, but in practice they are not much use for the Kremlin. American weakness has indeed created vacuums -- in the Middle East, in East Asia, in Latin America, and in Africa. But the story so far is that these are not opportunities that Russia can exploit.