CNOOC Ltd sent documents to banks containing proposed terms for a US$6 billion loan as it seeks to acquire Canada's Nexen Inc in the biggest overseas takeover by a Chinese company, a person familiar with the matter said.

China's largest offshore oil and gas explorer has approached banks including lenders from Singapore, China, Australia, Europe and the US, the person said, asking not to be identified because the details are private. Citigroup Inc is CNOOC's financial adviser, the person said.

The Beijing-based company agreed to pay US$15.1 billion in cash in July to acquire Nexen. The energy firm said last week 99 percent of common shareholders voted in favor of the deal, which still needs approval from Canadian, US and UK governments.

Michelle Zhang, a spokeswoman for CNOOC, couldn't be reached for comment on the financing when called and e-mailed at her office yesterday.

CNOOC is offering to pay an upfront 25 basis-point fee for the 12-month facility with no limits on commitment size, the person said, citing details from the term sheet. The margin on the loan starts at 80 basis points over the London interbank offered rate for the first six months, before rising to 100 basis points for the next three months and 120 basis points for the final period, the person said.

Banks have been asked to respond by October 16, the person said. CNOOC is considering eventually refinancing the bridge loan with proceeds from a bond sale, two other people familiar with the matter have said.