Canada will send 3,000 metres of oil boom to help with cleanup efforts in the Gulf of Mexico. (CBC)

The Canadian Coast Guard will send at least 3,000 metres of oil boom to help with cleanup efforts in the Gulf of Mexico, Fisheries and Oceans Minister Gail Shea announced Sunday.

Shea said Canada had extended an open offer to help with recovery efforts since the spill began in April. The United States made a specific request for offshore oil boom on Friday.

The shipment represents about half the federal government's supply of offshore boom, Shea told a news conference in Dartmouth, N.S.

"We have to keep some in case we have to respond to spills here at home," she said, when asked why the entire supply was not being sent.

Shea said the cost of shipping and deploying the boom will be approximately $3 million. That cost will be recovered from the U.S. government.

The boom is in addition to technical and scientific support already being provided by Canada, Shea said.

Transport Canada has provided a Dash 8 aircraft, which has been assisting with aerial surveillance of the spill along the Louisiana coast since early May.

A Canadian marine aerial reconnaissance team is also in the area and experts from the Nova Scotia-based Centre for Offshore Oil and Gas Environmental Research are advising on the effectiveness of cleanup operations.