Fidelity Investments, in comment letters to US and international regulators this week, urged any international reforms of money market funds to be “carefully considered” to avoid “imposing harmful, unintended consequences on financial markets or on the global economy.”

The largest US manager of money market mutual funds, Boston-based Fidelity urged the International Organization of Securities Commissions to follow the US model of money market regulations and said the system has been working since the financial crisis.

Commenting on the commission’s consulting report on “Money market fund systemic risk analysis and reform options,” Fidelity wrote that the report “seems to presume that MMFs present risks to the financial system and that additional reform is needed. We do not agree with those presumptions, which are asserted, but unsubstantiated.”

Fidelity also lashed out at other, potentially riskier areas of the investment arena. The firm encouraged regulators to expand their focus beyond money market funds to examine hedge funds and other vehicles “that remain unregulated and non-transparent.”

“We recommend that international regulators concentrate on introducing regulation to the various pools, structured vehicles, and other funds that offer cash investment without the strict rules under which money market funds operate,’’ one of the letters, dated May 30, said.

The US federal government provided special guarantees for money markets during the financial crisis, to help restore confidence to the system after a handful of funds struggled to maintain their stable, $1 per share value.

Fidelity said it managed $415 billion in money market funds at the end of 2011, representing 16 percent of US investors’ assets in money markets and 9 percent of global money market assets.