But the group pledged to act individually and together to promote stability and growth.
It also urged banks to disclose all their losses and bolster their balance sheets to help stabilise markets.
The group's statement came after a day-long meeting of ministers and central bank governors in Tokyo.
"In all our economies, to varying degrees, growth is expected to slow somewhat in the short term," it said.
The G7 nations said that continuing risks included further problems for the US housing market, tighter credit, high commodity prices and rising inflation.
"Going forward, we will continue to watch developments closely and continue to take appropriate actions, individually and collectively, in order to secure stability and growth in our economies," they said.
They also called on oil producers to increase output and on China to let its currency appreciate faster.
US Treasury Secretary Hank Paulson said current financial turmoil was "serious and persisting".
"As the financial markets recover from this period of stress, as of course they will, we should expect continued volatility as risk is repriced," he said.
"As financial officials, we need to respond resolutely and proactively to the turmoil."
He did not suggest specific measures for G7 partners to take.
Mr Paulson said he was confident in the long-term health of the US economy and expected it to grow this year, but also said a recent stimulus package had been crucial.
The G7 countries include the US, Japan, the UK, Canada, France, Germany and Italy, all of which are experiencing a significant slowdown in growth.
Meanwhile, China, India and other East and South East Asian economies have experienced break-neck growth over the past few years as current account surpluses and foreign exchange reserves have ballooned.
But as the global credit crisis and US housing slump has brought the world's largest economy to its knees, concerns have persisted that these problems would spread to Asia, which is heavily reliant on US imports of its products and foreign investment for growth.
On Friday, Haruhiko Kuroda, the head of the Asian Development Bank, warned that the US economic downturn would take its toll on emerging Asian economies.
But he stressed that rising inflation in the region is currently more of a threat than worries about a slowdown.
More rate cuts?
Last week, the International Monetary Fund cut its global economic growth forecast from 4.4% to 4.1%, the lowest in five years.
Following aggressive interest rate cuts in the US and the approval of a bill giving Americans tax rebates worth $167bn (£86bn), the focus has been on whether other industrialised nations would implement stimulus plans of their own.
Perceptions have changed as to whether the European Central Bank (ECB) is likely to reduce interest rates from their current level of 4% to help boost growth in the euro zone.
ECB President Jean-Claude Trichet has previously maintained a tough line on controlling inflation in the 15-nation bloc that uses the euro despite clear signs that a frail recovery was running out of steam.
But following an ECB decision to keep rates on hold on Thursday, he appeared to shift focus, stressing the risks to the global economy in his press conference.
This raised hopes that euro zone interest rates could be cut later this year.
© BBC MMVIII