US producer prices unexpectedly fell in July, recording their biggest drop in nearly a year and pointing to a further moderation in inflation that could delay a Federal Reserve interest rate increase.

Other data today showed an increase in the number of Americans filing for unemployment benefits last week.

The trend in weekly jobless claims, however, remained consistent with a tightening labour market.

The Labour Department said today its producer price index (PPI) for final demand slipped 0.1% last month, weighed down by decreasing costs for services and energy products.

That was the largest decline since August 2016 and reversed June's 0.1% gain. In the 12 months through July the PPI increased 1.9% after rising 2% in the year through June.

Economists had forecast the PPI ticking up 0.1% last month and climbing 2.2% from a year ago.

Though the link between the PPI and the consumer price index has weakened, last month's drop in producer prices could worry Fed officials who have long argued that the moderation in inflation was temporary.

Fed Chair Janet Yellen told lawmakers last month that "some special factors" were partly responsible for the low inflation readings. Inflation, which has remained below the US central bank's 2% target for five years, is being watched for clues on the timing of the next Fed interest rate increase.

The US central bank is expected to announce a plan to start shrinking its $4.2 trillion portfolio of Treasury bonds and mortgage-backed securities at its policy meeting next month.

But low inflation, characterised by sluggish wage growth, suggests the Fed could delay raising rates again until December. It has increased borrowing costs twice this year.

Prices of US Treasuries rose after the data while the dollar pared gains against a basket of currencies.

US stock index futures were weaker as investors focused on continuing tensions between the United States and North Korea.

In another report today, the Labour Department said initial claims for state unemployment benefits increased 3,000 to a seasonally adjusted 244,000 for the week ended 5 August.

With the labour market near full employment, there is probably limited room for claims to continue declining.

Claims have now been below 300,000, a threshold associated with a healthy labour market, for 127 straight weeks.

That is the longest such stretch since 1970, when the labour market was smaller. The unemployment rate is 4.3%.

A tightening labour market and tepid inflation put the Fed in a difficult position.

Last month, prices for services fell 0.2%, the first decline since February. That accounted for more than 80% of the decrease in the PPI. Services were weighed down by a 0.5% drop in the index for final demand trade services. Services had increased for four straight months.

The cost of healthcare services rose 0.3% after being unchanged in June. Those costs feed into the Fed's preferred inflation measure, the core personal consumption expenditures price index.

Energy prices fell 0.3%, declining for a third straight month. Food prices were unchanged in July following a 0.6% jump in the prior month.

A key gauge of underlying producer price pressures that excludes food, energy and trade services was unchanged last month. The so-called core PPI gained 0.2% in June.

Core goods prices fell 0.1% in July after increasing for eight straight months. The core PPI increased 1.9% in the 12 months through July after advancing 2.0% in June.