WASHINGTON — President Barack Obama supports the decision by allies to send military advisers to aid Libyan rebels but has no plans to put US "boots on the ground," his spokesman said Wednesday.

A senior American diplomat, meanwhile, told lawmakers in a letter obtained by AFP on Wednesday, that Obama plans to provide the rebels with up to $25 million in urgent, non-lethal aid.

White House spokesman Jay Carney said Obama approved of France's decision to send military advisers into insurgent-held eastern Libya, with Britain and Italy set to follow suit.

"The president obviously was aware of this decision and supports it, and hopes and believes it will help the opposition," Carney told reporters aboard Air Force One en route to California.

"But it does not at all change the president's policy of no boots on the ground for American troops."

Embattled Libyan leader Moamer Kadhafi's government has warned that foreign boots on the ground will prolong the conflict.

A message from Acting Assistant Secretary of State for Legislative Affairs Joseph Macmanus to the US Senate Foreign Relations Committee, sent Friday, shows Washington stepping up its help to embattled opposition forces in Libya.

"I wish to inform you that the president intends to exercise his authority to draw down up to $25 million in commodities and services from the inventory and resources of any agency of the United States government," he wrote.

"The president's proposed actions would provide urgently needed non-lethal assistance to support efforts to protect civilians and civilian-populated areas under threat of attack in Libya," said Macmanus.

A memorandum attached to the letter said the aid could include vehicles, fuel trucks, ambulances, medical equipment, protective vests, binoculars, and radios.

The developments came as the besieged rebel-held city of Misrata desperately pleaded for help against Kadhafi's forces, who have been pounding it for more than six weeks.

The bombardment continued on Wednesday, with loud explosions heard mid-afternoon in Misrata, where there was heavy overnight fighting and from which thousands of people are trying to flee.