WASHINGTON (BLOOMBERG) - The Treasury Department stopped short of declaring China a currency manipulator in its semi-annual report on foreign-exchange rates, averting an escalation of a trade war while serving notice that the United States will closely watch the yuan after its recent slide.

"Of particular concern are China's lack of currency transparency and the recent weakness in its currency," Treasury Secretary Steven Mnuchin said in a statement. "We will continue to monitor and review China's currency practices, including through ongoing discussions with the People's Bank of China."

While Treasury said in the report that direct intervention by China's central bank has recently been "limited", the US is "deeply disappointed" that the nation does not disclose its foreign exchange intervention.

No major trade partner was designated a currency manipulator, according to the report, which was released on Wednesday (Oct 17) by the Treasury. Still, the department dialled up criticism of China's state-driven economic model.

"Real exchange rate movements in 2018 - particularly the strengthening of the dollar and the decline in China's currency - would, if sustained, exacerbate persistent trade and current account imbalances," according to the report.

The Treasury said China's economic model "which continues to rely significantly on non-market mechanisms, is posing growing risks to the long-term global growth outlook".

The decision not to label China a manipulator stands in contrast with public comments made by President Donald Trump, who has repeatedly accused China of gaming the value of the yuan to gain an advantage in trade.

While formally declaring China a manipulator would not have triggered sanctions or other US penalties, it would have worsened an already tense relationship between the world's two biggest economies.

Mr Trump has slapped tariffs on US$250 billion (S$344 billion) in Chinese goods and China has retaliated with tariffs on about US$110 billion of US products.

On top of the escalating trade war, Mr Trump recently accused China of meddling in the 2016 elections, as well as the upcoming midterms in November. Earlier on Wednesday, Mr Trump said he plans to withdraw from an agreement that allows Chinese shippers to send products to the US at discounted rates.

Mr Mnuchin has said since July that Treasury is concerned about the yuan's recent drop.

The currency has slid about 9 per cent against the dollar in the last six months, making it one of the worst-performing Asian currencies this year and raising speculation that China has been deliberately weakening its currency as trade tensions with the US worsen.

Mr Mnuchin determined in the report released on Wednesday that China has not crossed three thresholds set by Congress that determine whether a country should be formally designated a currency manipulator.

They include a minimum US$20 billion trade surplus with the US; a current account surplus in excess of 3 per cent of gross domestic product; and repeated interventions in currency markets.

"If they'd found a way to label China, it would have hurt sentiment further," said Mr Shahab Jalinoos, Credit Suisse Group AG's global head of FX trading strategy. "But this being a yawn, if anything it should make markets more comfortable" with emerging market risk.

The offshore yuan strengthened 0.1 per cent to 6.9243 per dollar as of 5.31pm in New York.

Treasury's currency watch list remained the same, naming China, Japan, South Korea, India, Germany and Switzerland.

The report also said the euro appears undervalued for some of the stronger economies in the currency bloc, including Germany, which Treasury said has a responsibility to rebalance global trade.

South Korea sold US$4.1 billion of its currency in the year through June, and Treasury called on Seoul to encourage domestic demand.

India now only meets one of the three criteria to be labelled a currency manipulator, compared with two in the April report. The country could be removed from the monitoring list next April.

The Treasury also remains concerned about the persistence of a large trade deficit with Japan, while the department urges Switzerland to boost transparency of its currency interventions.

Thailand was not added to the watch list, as some currency analysts had anticipated.

While Mr Trump in August said that the administration was looking closely at the criteria it uses to review currency policies, Treasury did not change its thresholds. It won't expand the number of countries it scrutinises, which it said it was considering in April.

But the department continues to review currency policies under both 1988 and 2015 trade acts.