The United States on Friday pressed China to improve communication of its economic policy and avoid competitive devaluations, as G20 finance chiefs met hoping to calm markets rattled by slowing Chinese growth and the prospect of a US rate hike.

The finance chiefs gathered for the two-day meeting in Ankara under Turkey's G20 presidency -- a role that in 2016 goes to China -- at a time of some alarming indicators from the global economy, in particular from key emerging markets.

A source close to the talks said that it is not likely the two major sources of concern -- China's slowdown and the US Federal Reserve's monetary policy -- will be directly referenced in the final communique.

"It's not the way things are done here" at the G20 said the source, adding it would be highly unusual for the statement, whose every word is negotiated months in advance, to refer to a specific central bank or country.

- 'No competitive devaluations' -

But US Treasury Secretary Jacob Lew met his Chinese counterpart Lou Jiwei on the sidelines of the meeting, urging Beijing not to devalue its currency in order to gain a competitive advantage for its exporters.

The Chinese central bank on August 11 devalued the yuan by nearly two percent, surprising markets and raising concerns about the effects of China's economic slowdown.

"China should allow its exchange rate to reflect underlying fundamentals, avoid persistent exchange rate misalignments, and refrain from competitive devaluation," a US Treasury spokesperson quoted Lew as saying.

The spokesperson added Lew also "underscored the importance of China carefully communicating its policy intentions and actions to financial markets".

In an unusually strongly-worded statement, Lew also noted that it was important for China to signal that it will allow market pressures to drive the yuan "up as well as down".

Lew said Chinese President Xi Jinping's visit to Washington later this month "is an opportunity to make progress on issues vital to our economic relationship".

The consequences of a slowing Chinese economy have already caused panic selling on global stock exchanges and a further sharp fall in the price of oil.

But a senior government source from a major European economy insisted there was "no sense that China is going to be put in the dock for the accused," adding China has to "communicate in a clearer way."

- 'Crisis proportions' -

As well as China, markets have also been shaken by uncertainty over the future monetary policy of the Fed.

Markets have for months been speculating about the possibility of a rate rise from the Fed's September 16-17 policy meeting, which could be justified on the grounds of the robustness of the US economy.

But a tightening of US monetary policy would also have the effect of hoovering up liquidity from the global economy -- bad news for key emerging markets like Brazil and Russia which are in a deep slump.

It would also be worrisome for host Turkey which has seen growth slow amid persistently high inflation and a sharp fall in the value of its currency.

The Turkish Lira on Friday hit a new low in value against the dollar, smashing through the 3.0 ceiling to hit 3.01 to the greenback, a loss on value of 1.25 percent on the day.

London-based consultancy Capital Economics said that on some measures the slowdown in emerging markets in the second quarter of this year means their growth is now not much faster than developed markets.

"In pretty much every case (in the second quarter), growth slowed and several major emerging markets, notably Brazil and Russia, are now in recession," its chief emerging markets economist Neil Shearing said in a note to clients.

The Institute of International Finance, an industry association, said the recent decline in equity and currency values in several emerging markets "has reached crisis proportions".

Even if the Fed were to postpone the mooted rate hike until later this year "it would provide only short-term relief", it added.

In a closely watched release, the US Labor Department said Friday the unemployment rate fell to 5.1 percent, the lowest since early 2008, but economists said the data would not push the Fed to raise interest rates.

US and European markets tumbled after the release, with investors apparently still uncertain over the Fed's intentions.