WELLINGTON, July 26 (Reuters) - U.S. Secretary of State Antony Blinken arrived in the island nation of Tonga on Wednesday, the latest senior U.S. official to visit the South Pacific, but said Washington's interest in the region was not due to China's growing presence.

Blinken held talks with Tongan Prime Minister Siaosi Sovaleni on the strategic importance of the Pacific region, ahead of visits to the South Pacific's two major powers New Zealand and Australia.

Blinken said in a press conference that the United States was committed to both Tonga and the broader Pacific Islands regardless of China.

"It is about the partnerships that we believe it's in our interest to build with countries throughout the Pacific," Blinken said.

However, China’s growing presence in the region, which saw it sign a security pact with the Solomon Islands last year, has fuelled concern in Washington and Canberra about Beijing’s ambitions and prompted Western aid and increased engagement.

Blinken said the US had no objection to engagements by other countries including China but there were concerns that investments needed to be transparent, undertaken according to the rule of law, with sustainable finance and with no strings.

"I think one of the things that we’ve seen is that as China’s engagement in the (Indo-Pacific) region has grown there has been some, from our perspective, increasingly problematic behaviour," he said.

Tonga is heavily indebted to Beijing and in the past there have been concerns about how Tonga will repay that debt.

Sovaleni said at the press conference that Tonga had this year started to pay down its debt and had no concerns about China and its relationship was currently around development issues such as infrastructure.

Blinken will officially opening the new US Embassy in the capital Nuku’alofa later on Wednesday before flying on to Wellington, New Zealand.

The U.S. Defense Secretary Lloyd Austin is visiting Papua New Guinea this week before heading to Australia where the largest ever Australia-US military exercise is due to begin. France’s President Emmanuel Macron is also in the region visiting French territories, Papua New Guinea and Vanuatu.