American lawmakers were not happy when then president Jimmy Carter switched diplomatic sides from Taipei to Beijing on January 1, 1979. Their response was the Taiwan Relations Act , which became law 40 years ago this week to preserve relations with the island. It was intentionally written in vague and ambiguous language, not entirely pleasing to any party, but drafted in such a way that it is tolerable. For all its flaws, it has ensured peace, security and stability across the Taiwan Strait – matters that United States President Donald Trump has to be ever mindful of as he pushes ahead with his country’s rivalry with China. In each of the three communiques China and the US have signed, in 1972, 1979 and 1982, Washington has recognised that there is one China and Taiwan is part of it. The Act maintains that position, but takes an approach widely viewed as “strategic ambiguity” through a pledge of military support including arms sales for the island and acknowledging its “governing authorities”. While successive American governments have been largely cautious about dealings with Taipei, Trump has been eager to improve relations and laws have been enacted to enable high-level diplomatic exchanges. The opening next month of a new consular building that will host nearly 500 staff is being portrayed as a symbol of the new-found ties. Beijing’s position is unequivocal: peaceful reunion of the nation is its goal, but should there be moves for independence on the island, it is willing to take it back by force. That may have seemed an idle threat four decades ago, when the nation was poor and its military weak, but times are markedly different. China now has the world’s second-biggest economy and the region’s most powerful defence force. It sailed the Liaoning aircraft carrier group through the Taiwan Strait last year and recently flew two warplanes to within 200km of the island, prompting protests from Taipei and Washington. In a show of support for Taiwan, a 26-member American delegation led by former House of Representatives speaker Paul Ryan will visit the island on Monday for the anniversary. The trip was announced after Taiwanese leader Tsai Ing-wen on Tuesday held a video conference with three prominent think tanks in Washington in a bid for continued US support for defence. But her calls and suggestions that the US is about to approve the sale of advanced fighter jets to Taiwan is at odds with the agreements that have been struck. So, too, has been allowing Tsai stopovers on American soil, as happened in Hawaii last month. Using the island as a bargaining chip in trade negotiations also makes no sense. Political trickery should have no part in the Taiwan issue; Trump should preserve the status quo.