NEW YORK (Dow Jones/AP) — In a sign that the US’s ability to finance its trade and current account deficits is in danger, a report out yesterday suggests US investors are starting to find confidence and value in foreign securities.Just as worrisome, foreigners, too, may be starting to lose their appetite for US securities.

According to a report from the Treasury Department, net foreign acquisition of long-maturity US securities, or net capital inflow, tumbled to $15.6 billion in December, down 82 percent from $84.9 billion in November. Meanwhile, the US trade deficit came in at $61.2 billion.

This “warns that a) foreigners are finding US asset markets a little rich and b) US investors may finally be more attracted to returns in offshore markets,” said Chris Turner, currency strategist at ING Capital Markets in London.

Net capital inflow represents money flowing into the US, while the US trade deficit represents money flowing out of the country. The best scenario for the economy is when the two balance each other.

But Turner and other analysts are quick to note that the data should be read as merely a rough guide. The report, they point out, is prone to volatility and upside revisions in future months. And, besides all that, one month’s data do not a trend make.

They also point out that the figures are a so-called lagging indicator from two months ago. Given that the dollar’s value against the euro and other rivals has been relatively stable since December, investors must still be buying dollar-based assets, though perhaps in investments other than long-term securities.

The dollar immediately fell against the euro and the yen after the report’s release, but the dip was rather modest, and the dollar’s losses were mostly reversed later in the session.

But yesterday’s data bring new urgency to how the US finances its deficits, and testimony from Federal Reserve chairman Ben Bernanke on Capitol Hill shows that politicians were already worried.

Bernanke was specifically asked by a senator whether he is concerned that US investors may be buying foreign-based assets instead of investing in home-grown assets.

Bernanke said no, that he believes it’s healthy for investors here to diversify their portfolios to include foreign assets, because it could encourage foreigners to do the same, investing more in the US.

The problem, though, is that for the US to finance its twin deficits, it needs foreigners to invest here more than the US invests abroad.