The White House on Friday ordered environmental regulators to review the effect that pesticides may be having on bees and other pollinators that have suffered significant losses in recent years.

Environmental advocates welcomed the plan but said it did not go far enough, noting that the European Union has already banned three common pesticides, known as neonicotinoids, on the basis that they were making bees sick.

Honey bees contribute $15 billion in value to US crops annually, and have suffered severe losses in recent years due to a phenomenon known as colony collapse disorder.

Scientists still do not fully understand why various types of bees and butterflies are dying, but research points to a combination of stresses, including parasites, pathogens and exposure to pesticides widely used in farming.

The government's new plan calls for the Environmental Protection Agency to "assess the effect of pesticides, including neonicotinoids, on bee and other pollinator health and take action, as appropriate," within 180 days.

The memo signed by President Barack Obama also called for a sweeping strategy to be produced across government agencies in the next six months that would protect pollinators by improving their habitat.

Measures include planting flowers along highways, landscaping federal facilities with plants that are beneficial to pollinators, and expanding pollinator habitat in conservation areas.

"Over the past few decades, there has been a significant loss of pollinators, including honey bees, native bees, birds, bats, and butterflies, from the environment," Obama said.

"The problem is serious and requires immediate attention."

The US Department of Agriculture also directed an extra $8 million toward a program in some midwestern states to cultivate new habitats for honey bees.

However, environmental groups said the measures fall short.

"President Obama's announcement on protecting pollinators does not go far enough," said Friends of the Earth president Erich Pica.

"The administration should prevent the release and use of these toxic pesticides until determined safe," Pica added, noting that the US should follow Europe's lead.

The European Commission has restricted the use of three pesticides belonging to the neonicotinoid family, known as clothianidin, imidacloprid and thiametoxam, for a period of two years.

The EPA website says the United States "is not currently banning or severely restricting the use of the neonicotinoid pesticides."

Instead, they are "being re-evaluated... to ensure they meet current health and safety standards."

Larissa Walker, who heads the Center for Food Safety's pollinator campaign, said the announcement was "on the right track," but expressed concern.

"Assessment and habitat building alone won't save our pollinators. We need decisive action on pesticides," she said.

"We look to the Obama administration for leadership that will have the lasting impact we need to keep our pollinator populations sustainable and healthy."