Australia, NZ dollars start big central bank week on back foot as tariff uncertainty mounts

SYDNEY, July 7 (Reuters) - The Australian and New Zealand dollars started a big central bank week on the back foot as investors braced for U.S. trade uncertainty that could linger for weeks now that there appears to be a delay in the tariff implementation date.

The Aussie AUD=D3 fell 0.5% on Monday to $0.6522, the lowest level in a week. It ended last week just 0.3% higher, with resistance heavy at an eight-month top of $0.6590.

The kiwi dollar NZD=D3 eased 0.4% at $0.6025, the lowest in almost two weeks. It finished last week just 0.1% higher, with stiff resistance at a nine-month peak of $0.6120.

President Donald Trump said the U.S. will start delivering tariff letters to other countries starting at 12:00 p.m. ET (1600 GMT) on Monday. Earlier, he said the higher rates would now take effect on August 1 rather than July 9.

"If we do get the letters this week, then August 1 is the deadline as opposed to the midnight on the day that (they) send them out. That ostensibly leaves some wiggle room for negotiations... but what it is going to do is wreck markets with uncertainty," said Ray Attrill, head of FX strategy at the National Australia Bank.

Indeed, shares fell across Asia, with Wall Street futures down about 0.5%. The two Antipodeans are often sold as proxies for risk assets.

Down Under, it is a big week for central banks, with both Australia and New Zealand set to announce their latest policy decisions. Markets have almost fully priced in a rate cut from the Reserve Bank of Australia on Tuesday with a 95% probability.

Analysts at ING said as RBA turns more dovish, it could hinder gains in the Australian dollar versus other major currencies, although against the greenback, it remains a U.S. tariff story.

"We expect AUD to lag behind NZD and potentially other high-beta currencies where there is less room for front-end rates to fall, such as SEK (the Swedish krona)," they said in a note to clients.

Across the Tasman Sea, the RBNZ will meet on Wednesday and is most likely to keep the cash rate steady at 3.25%. Swaps imply a probability of 81% for no move.