(Adds details from statement) ZURICH, Dec 18 (Reuters) - Swiss National Bank currency market interventions to rein in the Swiss franc appeared to wane in the third quarter, current account data released on Friday showed. The SNB vowed on Thursday to remain active and intervene when necessary to rein in the “highly valued” Swiss franc after Switzerland was labelled a currency manipulator by the United States Treasury. In the national financial account, the SNB reported a net acquisition of financial assets of 40 billion Swiss francs ($45.2 billion), reflecting intragroup lending as direct investment and the SNB’s purchases of foreign currency, booked as reserve assets. Reserve assets acquired during the quarter plunged to 12.7 billion francs from 57.2 billion francs in the second quarter but rose from 11.7 billion in the third quarter of 2019. Switzerland’s overall third-quarter current account surplus shrank by a quarter to 9 billion francs. “This decline was particularly due to the lower receipts surplus in trade in goods and services. In the case of the goods trade, the decline was attributable to gold trading,” the SNB said in a statement. Switzerland posted a 9.88 billion current account surplus in the second quarter. ($1 = 0.8853 Swiss francs) (Reporting by John Revill in Zurich and Thomas Seythal in Berlin; Editing by Michael Shields and Alexander Smith)