Uncertainty reigns as dollar languishes

NEW YORK (CNNMoney.com) -- The dollar continued to slide this week, as market uncertainty and worries about intervention by Japan and the United States held the currency market hostage.

The dollar index, which gauges the greenback against a basket of currencies, retreated to a low of 78.1, a level not seen since February. That's down from 83.2 at the beginning of the month, and far below the June high above 88.

But it's not a huge surprise that September has been a lackluster month for the dollar.

Hedge funds and other big money investors typically pour money into commodities following Labor Day, said Michael Woolfolk, senior currency strategist at Bank of New York Mellon. And that can take its toll on the U.S. currency, since commodities like gold, oil and grains are priced in dollars.

It's also not unusual for the dollar to weaken when the stock market is on the kind of tear it has been recently. All three major U.S. indexes are on track to end September with gains - an unusual feat.

While the U.S. dollar continues to languish, the euro has been holding up fairly well despite some dour economic news.

The move by Moody's to downgrade Spain's sovereign debt rating, and continuing worries about the state of Ireland's economy has done little to weaken the euro.

Kathy Lien, director of currency research at Global Forex Trading, has even gone so far as to call the euro the "Teflon currency."

"You can throw almost anything at the euro these days and there is a good chance the Teflon currency will shrug it off," Lien wrote in a note to investors.

Meanwhile, the Chinese yuan was back in the news. On Wednesday, U.S. lawmakers said China's currency is unfairly cheap and passed a measure that opens the door to tariffs that aim to help U.S. companies compete.

The legislation, which authorizes the Commerce Department to impose duties on imports from countries with undervalued currencies, passed the House of Representatives but the Senate isn't expected to take up the measure until later this year.

The decision is not driving the currency market, because the congressional action doesn't come as a huge shock, said Kevin Chau, a currency analyst at IDEAGlobal.

Instead, traders are paying more attention to the yen, Chau said. The Japanese Foreign Ministry said it sold 2.12 trillion yen between Aug. 30 and Sept. 28 in an effort to weaken its currency, which recently was hitting 15-year highs and threatening the profitability of Japanese exporters.

There continues to be speculation that Japan may take additional action as early as next week, which some currency strategists think is a likely scenario.