Lloyd Austin is planning to meet President Volodymyr Zelensky and Defence Minister Andriy Taran, less than two months after both came to Washington to meet President Joe Biden, seeking assurances of US support.

Underscoring the US commitment, a fresh tranche of lethal arms and other military equipment was delivered Monday to Ukraine, part of a $60 million package the Biden administration approved.

That is designed to help Ukraine forces maintain their strength against Russia-allied rebels in the country's east, in a seven-year-war that has cost 14,000 lives.

But the main point of Austin's visit, a senior US defence official said, is to emphasise the need for more reforms, in regularising the defence industry, strengthening human resources development in the military, and deepening civilian control of the armed forces.

The human resources reforms are highly important in building the Ukraine military's ability to work closely with NATO, as it seeks membership in the Atlantic alliance.

"The Ukrainian government is committed to advancing these reforms," the official said, adding: "We need to enhance Ukraine's civilian control of the military."

The meetings Tuesday are a "high priority" for the Pentagon, the official said.

"It was important for us to show the Ukrainian people that we are here standing beside them."

Austin's visit is part of a three stop tour of countries on the rim of the Black Sea -- the others are Georgia and Romania -- which feel threats from Russia and whose militaries coordinate with NATO.

On the visit to Washington at the end of August, the two sides called bilateral relations "stronger than ever" and finalised a Strategic Defense Framework.

But Washington continues to be frustrated by extensive corruption and political turmoil in Ukraine.

"We are encouraging their defence reforms to enable their resilience in the face of this Russian aggression," the official said.