Foreign policy: From olive branch to big stick BARACK OBAMA, Washington greybeards used to say, differs from other American presidents: he secured a place in world history merely by being elected. The agreed wisdom was that Mr Obama might thus devote his final, lame-duck years to domestic matters - unlike predecessors who headed abroad to escape frustrations at home. However, after Republicans seized control of Congress, threatening to hobble much of the Obama agenda, it was with almost visible relief that the president flew off for back-to-back summits in China, Myanmar and Australia, swiftly agreeing with China that both countries should cut greenhouse-gas emissions (see article) and that both would back world trade talks to scrap tariffs on 200 categories of high-tech gizmos. Yet Mr Obama cannot escape questions about how much Congress will let him do. Though presidents have wide foreign-policy powers, the Senate must ratify new treaties, and congressional control of spending gives members great sway. On some dossiers, the next Congress may be rather helpful. A Republican Congress is more likely to back free-trade pacts that America is seeking with 11 Asia-Pacific countries and (a longer shot) with the European Union. An important moment will come when members are asked to grant the president fast-track authority to negotiate pacts that Congress may then either vote up or down, but not amend. Those allies who fret about America turning inward may cheer to see Republicans in key committees trying to restore some funds cut from the Pentagon's budget, pushing for rebels in Syria to receive more help and backing more ambitious moves against Islamic State (IS). Senator John McCain of Arizona, who is in line to chair the Senate Armed Services Committee, has demanded arms for Ukraine in its fight against Russian-backed separatists, as well as tougher sanctions against Russia. Some colleagues are more cautious. Any congressional action will not be swift. In other areas Congress may quickly prod Mr Obama in ways that allies (notably in Europe) will dislike. Start with negotiations to curb Iran's nuclear ambitions. An interim agreement struck by America, Russia, China, France, Britain and Germany to freeze bits of Iran's nuclear programme in exchange for sanctions relief is likely to be extended after it expires on November 24th. Republicans and some Democrats in Congress have long worried that Mr Obama might strike a weak deal with Iran, and drafted bills that sought to stiffen the president's spine by setting out sanctions that could either be added or reimposed if Iran backslides. The White House believes that the president can use his executive powers to suspend many sanctions, though only Congress can revoke sanctions that it has passed. For months administration officials have accused Congress of risking war with Iran if talks fall apart, and Democratic control of the Senate has - until now - prevented hawkish Iran bills from coming to a vote. After January, when Republicans take charge, Mr Obama will lose that firewall, potentially forcing him to veto bills he dislikes. Advocates of a tough line on Iran call such pressure beneficial. They note that Senator Bob Corker of Tennessee, the likely new Republican chairman of the Senate Foreign Relations Committee, is a consensus-builder who says he wants to see Congress sternly scrutinise any Iran deal, but is no warmonger. Expect a Republican Congress to state more explicitly its view of what constitutes a good Iran deal, says Michael Singh of the Washington Institute for Near East Policy, a think-tank. As for Israel, that country has long enjoyed bipartisan support in Congress, he adds. With Republicans in charge, members will show "less deference" to the president when he disagrees with the Israeli prime minister, Binyamin Netanyahu. A debate looms about the president's legal authority to use military force and rally allies against the extremists of IS. Though Mr Obama says he can use a war-authorisation law passed after the September 2001 attacks, the president and Republican leaders agree that Congress should update the legal underpinnings of what looks like a long fight. Confrontations are possible over Cuba policy, with Republicans resisting steps to ease the embargo on that country. Mr Obama wants to close the Guantánamo Bay prison camp for terror suspects, but Republicans are opposed. The window for constructive co-operation will close as the 2016 election nears, and debates about Mr Obama's first-term policies towards Russia, Myanmar or Libya become chances to attack Hillary Clinton, his first secretary of state and a putative presidential candidate. At that point, a lame-duck president may find his wings truly clipped.