Aussie benchmark on track for best month since July 2016 U.S....

• Aussie benchmark on track for best month since July 2016
• U.S. top trade negotiator cautions on trade deal
• Rio shares at more than decade high after 2018 results

Australian shares were mostly flat on Thursday as investor caution towards a resolution to the U.S.-Chinese trade war kept a cap on sentiment, however, the benchmark index looks set to post its best monthly gain in years.

The S&P/ASX 200 index (xjo) was largely flat at 6,152.4 by 0150 GMT. The benchmark is on track to gain roughly 4.9 percent in February, which would be its biggest monthly percentage gain since July 2016.

Denting a recent revival investor confidence, U.S. Trade Representative Robert Lighthizer said on Wednesday it was too early to predict an outcome in U.S.-China trade talks.

"Trump's adviser Lighthizer has poured a little bit of cold water through the comments about the Chinese trade tariff deal," said Damian Rooney, director of equity sales at Argonaut, saying that the deal markets have been hoping for may take a little longer.

On Thursday, the mining index .AXMM fell 0.2 percent, with iron ore miner Fortescue Metals Group (FMG) , trading ex-dividend, down over 4 percent and among the biggest losers.

Bucking the trend, Rio Tinto (RIO) touched a more than 10-year high after posting its highest annual underlying earnings since 2014 and announced a bumper dividend after market hours on Wednesday.

Gold prices also fell on Wednesday, pressured by a mild revival in the U.S. dollar after comments from the U.S. Trade Representative.

Newcrest Mining (NCM) fell 0.8 percent, while smaller peers St Barbara (SBM) and Resolute Mining (RSG) dropped 1.4 percent and 2.4 percent, respectively.

Energy stocks were supported by rising oil prices. The energy sub-index .AXEJ added 0.3 percent.

Elsewhere, Bingo Industries Ltd (BIN) rose as much as 27.6 percent, its biggest intraday percentage gain, after announcing a share buy back of up to A$75 million.

New Zealand's benchmark S&P/NZX 50 index (nz50) rose 0.4 percent, or 32.91 points, to 9,316.09.

Gains from Fisher & Paykel Healthcare (FPH) and Spark New Zealand (SPK) offset a more than 4 percent drop in dairy giant Fonterra's (FSF) , which cut its annual guidance.