* TSX ends down 0.9% at 19,754.14

* Posts its lowest closing level since June 1

* Energy retreats 2.1%; oil settles 1.8% lower

* Materials group falls 2.6%

June 20 (Reuters) - Canada's resource-heavy main stock index fell on Tuesday to its lowest closing level in nearly three weeks as weaker commodity prices weighed on resource shares ahead of possible clues on the interest rate outlook.

The Toronto Stock Exchange's S&P/TSX composite index ended down 180.07 points, or 0.9%, at 19,754.14, a closing low last reached on June 1.

Wall Street stocks also lost ground, with Federal Reserve Chairman Jerome Powell's congressional testimony on Wednesday looming as a potential market mover.

Also on Wednesday, the Bank of Canada will release minutes for its policy decision two weeks ago when it hiked its benchmark rate for the first time since January.

"There's a feeling that now they're going to raise until something breaks because things have not broken yet ... employment numbers are still strong and people are still able to finance their mortgages," said Diana Avigdor, portfolio manager and head of trading at Barometer Capital Management.

The energy group lost 2.1% as oil settled 1.8% lower at $70.50 a barrel.

"Crude prices are lower on disappointment with the size of cuts with China's key lending rates," Edward Moya, senior market analyst at OANDA, said in a note.

Canada will fall short of reaching net-zero emissions by 2050, unless it takes actions beyond the efforts already underway, the Canada Energy Regulator (CER) said.

The materials group, which includes precious and base metals miners and fertilizer companies, lost 2.6% as gold and copper prices fell, while heavily weighted financials were down 0.8%.

Canada's financial regulator said it was raising the amount of capital the country's biggest lenders must hold as a stability buffer by 50 basis points to 3.5%, citing rising borrowing costs, high debt levels and stress on the financial system. (Reporting by Fergal Smith in Toronto and Ankika Biswas in Bengaluru; Editing by Shilpi Majumdar and Richard Chang)