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WASHINGTON — Transportation Secretary Ray LaHood rejected raising fuel taxes to pay for highway improvements and said that, despite pessimism about the prospects for a long-term highway bill, the administration was focused on completing a bill this year.

The U.S. trade deficit widened 4.8% in May to the highest level in a year and a half, the Commerce Department said Tuesday.

Massachusetts has indefinitely suspended a 2% biodiesel mandate for fuel and heating oil that was to take effect this month, saying that without the federal tax credit for the producers, the cost of biodiesel would be too high for consumers.

The U.S. Environmental Protection Agency, noting “growing interest” in alternative-fuel conversion systems, recently proposed to streamline certification of aftermarket conversions that turn Class 8 diesel engines into engines that can burn diesel and natural gas.

The California Air Resources Board has awarded $200 million in Proposition 1B funds to help cut emissions from heavy-duty trucks and other sources in the state’s four busiest trade corridors.

A bipartisan group of U.S. senators left a closed-door White House meeting with President Obama last week divided over whether energy and climate legislation could pass and uncertain what form it might take.

A new study has found that nationwide adoption of a low-carbon fuel standard would increase the retail cost of motor fuel by as much as 170% over a 10-year period.

Retail diesel prices reversed course last week, as the national average rose 3.3 cents a gallon to $2.961 after falling 19.9 cents in the five previous weeks, the Department of Energy reported.

The National Highway Traffic Safety Administration plans to propose fuel efficiency standards starting with model year 2016 commercial medium- and heavy-duty on-highway vehicles, and said it will prepare and environmental impact statements as part of the procedure.