CSIRO chief executive Larry Marshall remains optimistic about collaboration between the CSIRO and the US scientific community despite US President Donald Trump's plan to cut funding to some of CSIRO's key US partners.

Dr Marshall was speaking at a business briefing in Sydney on Friday organised by the American Chamber of Commerce in Sydney.

In his speech, Dr Marshall said that the US was CSIRO's most significant international research partner, highlighting relationships with partner organisations NASA, Boeing, GE and NOAA, the National Oceanic and Atmospheric Administration.

In March, Mr Trump released his "America First" budget, which proposes to cut NOAA's research budget by 52 per cent, NASA's earth science budget by 5 per cent and the Environmental Protection Agency's research and development office by 48 per cent, according to the American Association for the Advancement of Science.

Dr Marshall said he wasn't worried about what might happen. "We've been in the US for a long time. We've navigated many changes in government and policy. The world needs science and the US needs it as much as anyone else does. So I'm optimistic."

At the business briefing, Dr Marshall announced that CSIRO has signed a five-year $35 million dollar research agreement with Boeing, the world's largest aerospace company.

The deal extends 28 years of co-operation between Boeing and CSIRO.

Dr Marshall announced the agreement while outlining CSIRO's plans for developing scientific co-operation in the US.

"Adopting a global outlook for national benefit is a key pillar of CSIRO's strategy – and it's an approach that has yielded enormous benefits through our relationship with Boeing," Dr Marshall said.

Dr Marshall said 23 per cent of CSIRO's total revenue in 2011-2015 came from international sources and said that was set to rise to 33 per cent of our future revenue for 2015-2020.

Boeing employs 3500 people in Australia manufacturing parts of the Dreamliner aircraft, and working on projects in space sciences, military and materials science.

Dr Marshall told the luncheon that CSIRO would be expanding its efforts to support new technology and start-ups in Australia reach US markets.

In January, Dr Marshall announced CSIRO would open an office in California's Silicon Valley.

On Friday Dr Marshall said the San Mateo office "will provide a base for visiting researchers, new business spin-outs and innovators for our commercialisation pipeline".

Dr Marshall said that by 2020, "we want working with CSIRO to be synonymous with a game plan for entry into the US market."

CSIRO scientists have expressed concerns that Dr Marshall's concentration on commercialisation will detract from the public good research science undertaken by CSIRO.

Nigel Warren, general manager of CSIRO global, dismissed that concern, telling Fairfax Media that a staff of four in Silicon Valley out of a total of 5000 CSIRO employees showed that focus on scientific research continued.

The Australian start-up community will want to know exactly what CSIRO can offer it for plans to enter the US market, said Monica Wulff who runs start-up survey, Startup Muster.

"I think most Australian start-ups would be intrigued about CSIRO's plans in this space. I don't think there would be criticism yet, but the sector will want to know what CSIRO's motivation is."

Ms Wulff said: "Does CSIRO understand the needs of the Australian start-up system and what America can provide for them?"