Democrats and Republicans remained far apart on ending the government shutdown, let alone reaching a deal on the U.S. borrowing limit by October 17 to avoid an unprecedented default.
Republican House Speaker John Boehner vowed not to raise the debt ceiling without a "serious conversation" about what is driving the debt, while Democrats said it was irresponsible and reckless to raise the possibility of a default.
The comments appeared to mark a hardening stance since late last week when Boehner was reported to have told Republicans privately that he would work to avoid default, even if it meant relying on the votes of Democrats, as he did in August 2011.
The U.S. Standard & Poor's 500 e-mini futures shed 0.7 percent in Asian trade on Monday, pointing to further weakness on Wall Street later in the day. The S&P 500 index ended down 0.1 percent last week.
U.S. Treasury futures rose 5-1/2 ticks.
Selling of riskier assets has been orderly so far, but investors expect volatility to increase if the shutdown continues as the Oct 17 deadline gets closer.
"As the days tick by and the U.S. government's cash gradually starts to run out, the stakes will rise considerably," analysts at ANZ said in a note.
MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.5 percent, and its 12-month forward price-to-earnings ratio stood at 11.8, below a 10-year average of 12.4, according to Thomson Reuters Datastream.
Japan's Nikkei share average dropped 1.1 percent, extending last week's 5 percent tumble - it biggest weekly fall since early August.
NERVE TESTING TIME AHEAD
"A higher risk of a U.S. sovereign default would lead to a flight to liquidity and, ironically, a stronger U.S. dollar, except against the most liquid/safest-haven ones: euro, yen, sterling and Swiss franc," analysts at Barclays Capitals wrote in a note.
"That is not to say we expect a breach of the ceiling, and continue to expect that a resolution will be found, despite the brinkmanship."
The dollar slipped 0.4 percent to 97.05 yen, giving up its gains on Friday to snap a five-day losing run against the Japanese currency.
The greenback was down 0.1 percent against the euro at $1.3572. Against a basket of major currencies, the dollar eased 0.1 percent to be within striking distance of an eight-month trough hit last week.
Brent crude eased 0.3 percent to around $109.10 a barrel, after gaining 0.8 percent last week to end a three-week losing run.
Gold, a safe-haven investment, inched up 0.1 percent to about $1,311.7 an ounce.