SINGAPORE, Nov 28 (Reuters) - Interbank rates in Hong Kong hit two-decade highs on Tuesday, suggesting outflows are draining cash from the financial hub.

The benchmark one-month Hong Kong interbank offered rate jumped 5.6 basis points (bps) to 5.59012%, its highest since late 2000.

Two-month, three-month and six-month rates also hit 23-year highs.

Hong Kong rates are tethered to those in the U.S. because of the Hong Kong dollar's peg to the U.S. dollar.

However, over the past two weeks Hong Kong's rates have climbed -- even as wagers have firmed on U.S. rates having peaked -- pointing to capital outflows as Hong Kong and Chinese markets have been left behind in a strong rally for global stocks.

The milestone highs in interbank rates also come alongside a decline in the aggregate balance -- a gauge of cash balances in the Hong Kong banking system -- which at just above HK$45 billion is not far from its lowest level since 2008.

The city's currency is pegged to the greenback in a tight range of 7.75-7.85 per dollar. It hit its strongest in almost year on Monday at 7.7860 per dollar and weakened slightly to 7.7946 per dollar on Tuesday. (Reporting by Tom Westbrook; Editing by Kim Coghill)