President Barack Obama devoted just one sentence in last week’s State of the Union address to call for a new transatlantic trade and investment deal. However, if negotiated with sufficient ambition and presidential engagement, it is Obama’s best chance yet at leaving a positive foreign policy legacy.

The other global issues Obama catalogued in his speech were largely about avoiding the worst: North Korea, cyber threats, Iran, Syria and other Middle Eastern upheavals.  Achieving what Obama called “a Transatlantic Trade and Investment Partnership,” however, has all the makings of grand strategy.

It is about nothing less than combining the world’s two largest economies and communities of common interest in a manner that could reshape all global trade and investment standards. It would also reinvigorate the Cold War’s victors, known then as “the Free World,” at a new inflection point of history. Only through common cause can the United States and Europe ensure they continue to write global governance rules even as they lose relative power and influence to countries that are less committed to democratic rights and free markets.

The magnitude of U.S.-EU economic relations still has no rival. Despite the euro zone crisis and slow U.S. growth, the United States and the European Union still account for roughly 50 percent of the world’s gross domestic product and enjoy more than $3 trillion in cross-foreign direct investment. U.S.-EU trade in goods and services accounts for 40 percent of the world total, or $636 billion in 2011. The U.S. Chamber of Commerce reckons that figure could increase by $120 billion in the next five years  – if the two sides can eliminate tariffs.

Yet numbers don’t tell the whole story. A far-reaching trade and investment agreement would mark a transatlantic recommitment ceremony of historic significance, reversing a dangerous drifting apart.