U.S. business investment spending plans increased solidly for a second straight month in April, a hopeful sign for manufacturing activity after a long spell of weakness.

The Commerce Department said on Tuesday non-defense capital goods orders excluding aircraft, a closely watched proxy for business spending plans, rose 1.0 percent last month after an upwardly revised 1.5 percent increase in March.

The so-called core capital goods orders were previously reported to have increased 0.6 percent in March.

"It provides some indication that business capital investment activity might be on the mend," said Millan Mulraine, deputy chief economist at TD Securities in New York.

"However there is still a long way before we can get the necessary confirmation that the overall economic recovery is truly on track."

Business spending has slackened as a sharp decline in energy prices forced oilfield companies, including Schlumberger and Halliburton, to slash their capital expenditure budgets. Investment has also been undermined by a strong dollar, which has squeezed profits of multinational corporations.

The rebound in business spending, together with a sturdy labor market and firming underlying inflation, should keep the Federal Reserve on course to raise interest rates later this year.

U.S. government debt prices trimmed gains on the data. The dollar rose against a basket of currencies.

The increase in core capital goods orders offers cautious optimism that business spending outside the energy sector will pick up in the coming months and support manufacturing, and the broader economy, after a dismal first quarter.

Although order books at manufacturers remain lean, the core capital goods data corroborates other surveys, including one on small businesses, that showed a jump in capital expenditure plans in April and May.

Economic growth slumped early in the year and data so far on retail sales and manufacturing point to tepid economic activity early in the second quarter.

Economists polled by Reuters had forecast core capital goods orders gaining 0.4 percent.

Shipments of core capital goods, which are used to calculate equipment spending in the government's gross domestic product measurement, rose 0.8 percent last month after an upwardly revised 1.0 percent increase in March.

Shipments in March were previously reported to have increased 0.9 percent. Last month's increase in core capital goods shipments could see economists bumping up their second-quarter GDP growth estimates.

A 2.5 percent drop in transportation equipment, however, weighed down on overall orders for durable goods — items ranging from toasters to aircraft that are meant to last three years or more — which fell 0.5 percent last month.

Orders for machinery recorded their biggest gain in eight months in April and the increase in bookings for primary metals was the largest since September. While orders for computers and electronic products fell 3.6 percent, that followed a hefty 7.7 percent surge in March.

Orders for electrical equipment, appliances and components dropped 1.5 percent after gaining 0.9 percent the prior month.