Ford Motor Co (F.N) on Wednesday joined rival General Motors Co (GM.N) in reporting higher-than-expected second-quarter profits, and in the next breath warning of a rougher ride for the rest of the year.

Ford said full-year pre-tax profit, automotive operating margins and cash flow would be lower than 2016 results, sending the company's shares down 1.8 per cent in mid-day New York trading.

Rival GM on Tuesday reported headline profits that beat analysts' estimates, but warned that profits for the second half of the year will likely be lower than the first half, as the company scales back scale back North American production to cut its burgeoning inventories.

Ford and GM's results present a counterpoint to other big U.S. companies reporting strong profits, including heavy equipment maker Caterpillar Inc (CAT.N), aircraft maker Boeing Co (BA.N) and telecommunications power AT&T Inc (T.N).

Investors worry that for Detroit's automakers, the second quarter marks a peak and profits are headed downhill. Thousands of workers at GM's U.S. factories are dealing with short- and long-term layoffs as production of slow-selling sedans is throttled back.

Dearborn, Michigan-based Ford reported second-quarter net income of US$2.04 billion, or 51 cents per share, up from nearly US$2 billion, or 49 cents per share, a year earlier. A big contributor to that improvement was not higher profits on selling cars, but a lower tax rate of 15 per cent, half the level analysts had expected.

Excluding one-time items, Ford earned 56 cents a share, and on that basis analysts, on average, looked for 43 cents.

Ford's global sales were down 43,000 vehicles in the quarter, with 8,000 of that coming in the U.S. market. Ford said its full-year margin in North America would be lower than in 2016 due to US$1.2 billion in additional commodity costs, costlier price cuts and engineering expenses.

Ford's new Chief Executive, Jim Hackett, on Wednesday promised investors a rethink of Ford's spending, marketing and investment strategy within his first 100 days.

"The new reality is we really have to ask ourselves what do we have to believe to get the returns that we expect,” Hackett said.

Ford forecast full-year adjusted earnings per share in a range from US$1.65 to US$1.85, above the US$1.51 expected by Wall Street, according to Thomson Reuters I/B/E/S. However, the company has already booked 96 cents a share in adjusted profit - more than half its full-year target. GM has also generated more than half its full year target of US$6 to US$6.50 a share.