ASX mining shares are in the red on Tuesday with the S&P/ASX 200 Materials Index (ASX: XMJ) down 0.24% while the S&P/ASX 200 Index (ASX: XJO) is up 0.47%.

ASX mining stocks are struggling amid concerns about the sluggish Chinese economy.

The materials index has lost 4.58% in value over the past five trading days alone.

Why are investors nervous about ASX mining shares?

Investors are desperate for details regarding new stimulus measures flagged by China last week.

They're also concerned about how Donald Trump's proposed 60% tariff on Chinese goods imported into the US may impact the Chinese economy and, by extension, demand for Australian resources like iron ore.

Meantime, Morgan Stanley and Bell Potter have updated their ratings on various ASX mining shares.

According to The Australian, Morgan Stanley analysts Rahul Anand and Shannon Sinha said:

As the market awaits visibility on tariff risk versus China stimulus benefits, we see opportunities for exposure to resources as many stocks are skewed to the upside from a risk-reward perspective.

Let's check out three mining stocks that these brokers are backing for growth in an uncertain climate.

3 ASX mining shares to buy now: brokers

Pilbara Minerals Ltd (ASX: PLS)

ASX lithium mining share Pilbara Minerals is trading 0.23% lower at $2.19 on Tuesday.

Morgan Stanley has raised its rating on Pilbara Minerals to overweight.

However, the broker has cut its 12-month share price target by 15% to $2.55.

This still leaves a decent potential upside of 16% for investors who buy Pilbara Minerals shares today.

Bellevue Gold Ltd (ASX: BGL)

This ASX gold mining share is trading down 2.25% at $1.22 on Tuesday.

Bell Potter has initiated coverage on Bellevue Gold shares with a buy rating.

The broker has placed a 12-month share price target of $1.95 on the gold miner.

This implies a potential upside of 60% over the next 12 months.

South32 Ltd (ASX: S32)

This diversified ASX mining share is an outlier among its peers on Tuesday.

The South32 share price is trading 1.19% higher at $3.41 at the time of writing.

Morgan Stanley has raised its rating on South32 shares to overweight.

It has also upped its 12-month share price target by 19% to $3.90.

If the broker is right, investors who buy South32 shares today will see a 14% gain over the next year.