Ho Chi Minh City, Oct 16 (IANS): US Secretary of Defence James Mattis arrived here on Tuesday where he will meet his Vietnamese counterpart to strengthen security cooperation between the two countries.

Mattis told the media that Vietnam was growing as a partner of the US in defence during his second visit to the country this year after visiting Hanoi in January, reports Efe news.

Experts have said that the trip is part of the US plan to include Vietnam in a defence cooperation network to deal with regional security challenges, including Chinese assertiveness in the South China Sea.

Vietnam and China are involved in a dispute along with Brunei, the Philippines, Malaysia and Taiwan regarding sovereignty over territory in the South China Sea, one of the main conflicts in southeast Asia.

The secretary will also visit the former US air base Bien Hoa, where the US Agency for International Development has kicked off a project to clean-up Agent Orange, a toxic herbicide used by the US during the Vietnam war.

"This is America keeping her promise to remediate some of the past. But we are also looking toward the future. And the legacy of the war has turned into, actually, a basis for defence cooperation," Mattis said.

Military cooperation between the US and Vietnam has strengthened in recent years with multiple meetings between high-level officials and the historic visit of the aircraft carrier USS Carl Vinson, the first to dock at a Vietnamese port since the war, to Da Nang in March.

After his Vietnam visit, Mattis is set to travel to Singapore where the Asean Defence Ministers' Meeting is due to begin on Thursday.

He had also planned to visit Beijing but the trip was cancelled.