Australia's government on Sunday defended its response to China's courtship of nearby Solomon Islands which culminated in a security pact, ahead of a general election next month where it had hoped to highlight its national security credentials.

Defence Minister Peter Dutton in a television interview attributed China's success to an uneven playing field involving tactics with which no Australian government could compete.

The pact, announced earlier this month, is seen as a major inroad for China in the resource-rich Pacific, where the United States has long been the dominant influence along with allies Australia and New Zealand.

China has said the pact will help the Solomon Islands maintain social order and cope with natural disasters and humanitarian relief. It said it poses no risk to the U.S., while the Solomon Islands said it will not undermine regional peace.

Still, the U.S. has said it would respond accordingly to any Chinese military presence in the region, while critics of Prime Minister Scott Morrison have called the pact Australia's biggest diplomatic failure in the Pacific since World War Two.

Dutton, in an interview with Sky News, said the pact follows a pattern of China's engagement around the world.

"If you look at what's happened in Africa, there are corrupt payments being made - we could never compete with that sort of playbook," Dutton said, without providing evidence.

He said he could not comment on whether corrupt payments had been made in the Solomons case.

"China's incredibly aggressive - the acts of foreign interference, the preparedness to pay bribes to get outcomes, and to beat other countries to deals - that's the reality of the modern China."

Speaking to journalists later in the day, Morrison said China building a military base on the Solomon Islands would be a "red line" for Australia.

"Working together with our partners in New Zealand and of course the United States, I share the same red line that the United States has when it comes to these issues," ABC News quoted the prime minister as saying.

"We won't be having Chinese military naval bases in our region on our doorstep."

The embassies of China and the Solomon Islands in Canberra did not respond to requests for comment outside business hours.

Morrison looked to deflect criticism by shifting the debate to his economic policy, promising to not introduce any taxes if re-elected, and to cap government tax revenue at 23.9% of gross domestic product.

The policy also involves giving workers A$100 billion ($72.4 billion) in tax relief over the next four years.

Australians head to the polls on May 21. ($1 = 1.3816 Australian dollars) (Reporting by Praveen Menon; Editing by Christopher Cushing)