The bilateral meeting between Mattis and Ms Sitharaman will take place on the sidelines of the Association of Southeast Asian Nations Defence Ministers' Meeting in the Philippines that begins today and ends on October 25.
"I will have meetings while I'm in the Philippines at the ASEAN meeting with regional counterparts - Japan, the Republic of Korea, the Philippines of course, India, Indonesia, and Malaysia," Mattis told reporters travelling with him to Philippines.
This would be the first meeting between the two leaders after Mattis' successful trip to India last month.
Mattis said the ASEAN defence ministers' meeting will be an opportunity to recognise ASEAN for 50 years of promoting peace and stability in the region.
"They have done a very good job of it. Nations coming of age, many years finding, finding, basically a foundation where they can discuss things," he said.
ASEAN, he said, provides an international forum, giving voice to those who want relations between states to be based on respect, not on predatory economics or on the size of militaries, in an apparent reference to China.
"ASEAN nations have demonstrated that they can listen to one another, they identify opportunities to increase defence cooperation for their own security, and seek shared solutions to shared concerns," he said, adding that the US remains unambiguously committed to supporting ASEAN.