The ongoing trade battle between the US and China poses a major threat to efforts to tackle inequality and poverty, according to billionaire philanthropist Bill Gates.

In an interview with the Guardian, the world’s second richest man said the economic conflict between the two superpowers could prove a “real setback” to solving some of the biggest global problems.

“With the US-China relationship, if that really breaks down then that hurts the world economy and hurts the world’s ability to work together,” said Gates.

“So that’s a real setback. I’m a huge believer in rich countries working together, especially when it’s to help poorer countries. But I don’t think the rise of this populist ‘every country for themselves’ rhetoric is the full picture.

“I’m not trying to say we should ignore the rhetoric, but its partly that people don’t see that the co-operative efforts have had great results.”

Speaking ahead of next week’s annual Bill & Melinda Gates Foundation’s goalkeepers event in New York, celebrating progress in global development during the annual gathering of world leaders at the UN general assembly, the Microsoft founder admitted that the ambitious targets set at the UN in 2015 “are looking unlikely” to be met.

The 17 sustainable development goals, committed to by 193 world leaders four years ago, are a series of objectives to achieve three things by 2030: end poverty, fight inequality and injustice, and fix climate change.

In the foundation’s own third annual goalkeepers data report, released this week, the data shows progress is being made on health and development, but that inequality remains a major barrier.

“Its definitely a mixed story,” said Gates. The report shows vast improvements being made in child mortality around the world. Even in the worst-off parts of low- and low-middle-income countries, more than 99% of communities have seen an improvement in under five death rates and in schooling.

But persistent gaps in opportunity mean that nearly half a billion people – one in 15 – still do not have access to basic health and education, while inequality between boys and girls means development investments aren’t reaching everyone. Using new, sub-national data, the report uncovers vast inequalities within countries that have been masked by averages.

“Where you’re born is still the biggest predictor of your future, and no matter where you’re born, life is harder if you’re a girl,” said Gates.

Melinda and Bill Gates at a foundation event in New Delhi, India. Photograph: Manish Swarup/AP

Despite gains in female education, opportunities for girls are limited by social norms, discriminatory laws and policies, gender-based violence and access to reproductive healthcare.

But Gates resolutely refused to be pessimistic about progress.

“Our optimism is more because of our nature,” he said. “It’s a global consensus to help others, and in no sense do I discern [political] polarisation could really hurt the consensus to innovate on behalf of the poorest.

“The rhetoric in the US favours all of this ‘America first’ that has led the executive branch in the US to propose cuts to foreign aid, and even to effectively disengage budgets. That was very concerning, but what actually happened was that the congress chose not to cut. In the case of the medical research budget, they made a substantial increase.

“For example, when I called President Macron a year ago and asked him to host the Global Fund this year, I had to be frank and say I didn’t know if we’d get the increase [in cash] we needed to fight malaria, TB and HIV. I didn’t know if Germany were going to come in with the increase we were asking for, I didn’t know if we were even going to be successful in getting everyone to the table, but in fact we saw a meaningful increase in commitment.

“I can’t predict that this polarisation is going to go away, but I do predict that the human desire to help other people is not; it’s a very strong thing, and in the UK you have a powerful commitment to that. The Conservative party did preside over the aid budget going from 0.5% to 0.7% of gross national income, which was an amazing increase at a time when the budgets were tight. So while I know these things are up to the UK voters and the UK politicians, I haven’t seen that consensus that its important to help the poorest come apart.”

Gates said that while things were getting better for people worldwide, the key issue now was inequality within countries, which would only be exacerbated by climate change.

Bill and Melinda Gates will use the goalkeepers event to call for a new approach to development, targeting the poorest first, especially with healthcare, and supporting farmers to adapt to climate change.

“Its absolutely right that, over time, climate change will front substantial problems for developing countries. Most of the poorest in these countries are farmers, so temperature extremes, floods and droughts will affect their ability to grow food and feed their families. Most of the focus has been on migration, but the foundation is very involved in adaptation – where the weather patterns will affect the poorest, helping them adapt,” said Gates,whose foundation has come under fire in the past for its investment in fossil fuels.

Gates has said climate activists are wasting their time lobbying investors to ditch stocks, calling it a “false solution” that did not reduce emissions. They would do better to get behind the disruptive businesses like Beyond Meat and Impossible Foods, non-meat protein food companies he supports.

After the Guardian spoke to Gates it was announced that a goalkeepers invitation had been extended to India’s president, Narendra Modi – intended to recognise his work in bringing better sanitation to India, but deeply controversial because Modi is accused of human rights abuses in Kashmir.