The US on Thursday moved closer to placing sanctions on Turkey over its purchase of the Russian S-400 missile defence system, with a bipartisan bill that Congress is set to vote on next week. A Senate summary notes that the legislation “establishes mandatory sanctions on Turkey for its acquisition of the Russian S-400 air missile defence system as required by the Countering America’s Adversaries through Sanctions Act". Under the original sanctions law, which Congress passed in 2017, the president is required to impose sanctions on any country that engages in a “significant transaction” with the Russian defence sector. American officials and politicians worry that Turkey’s acquisition and use of the system could allow Russia to spy on US-made military hardware. Despite immense pressure from both Democrats and some of his closest Republican allies in Congress, President Donald Trump has resisted placing the sanctions on Turkey, even after <a href="https://www.thenationalnews.com/world/the-americas/us-warns-turkey-over-reported-s-400-test-but-stops-short-of-sanctions-announcement-1.1094677">Ankara tested the system over the Black Sea in October</a>. In response to Mr Trump’s inaction, the House of Representatives unanimously added an amendment to the defence bill in July further clarifying that the president must put sanctions on Turkey over the S-400 purchase. But the House legislation also gives Turkey an out by authorising the president to remove the sanctions if Ankara gets rid of the S-400 system. As the Senate is on board with the Turkey sanctions provision, president-elect Joe Biden will have little choice but to deal with the issue soon after he takes office next month. Mr Biden could take a leaf out of Mr Trump’s book and ignore the law, at the risk of bipartisan anger in Congress, or apply the sanctions. Mr Trump has threatened to veto the defence bill unless Congress uses it to repeal a law that provides legal immunity to online companies for content that users posts online. But both chambers passed their respective versions of the bill with a veto-proof majority: 295 to 125 votes in the House and 86 to 14 in the Senate.