The Nikkei 225 index at the Tokyo Stock Exchange was up 31.30 points or 0.36 percent at 8,824.35 after the first 50 minutes of trading. The market was under pressure due to growing concerns over Portugal, Hideyuki Ishiguro, supervisor of investment strategy at Okasan Securities, said after the country's borrowing costs reached euro-era highs on Monday. The yen's strength will also likely weigh on major Japanese exporters, he told Dow Jones Newswires. But "players are not in panic mode, unlike last year", he said. "Trading may be subdued, but a selloff is unlikely." Government data released before the opening bell showed Japan's industrial output fell 3.5 percent in 2011 on the previous year after the March earthquake and tsunami disrupted supply chains, but rose by 4.0 percent in December alone. Japan's jobless rate edged up to 4.6 percent in December from 4.5 percent in the previous month while household spending rose 0.5 percent, the first increase since the disaster. The euro bought $1.3151 and 100.43 yen in early Asian trade, compared with $1.3134 and 100.34 yen in New York late Monday. The dollar rose to 76.35 yen from 76.67. The Japanese currency soared overnight as investors shunned risks and bought it as a safe haven. European Union leaders closed one chapter in the debt crisis late Monday with a new treaty supposed to end deficits -- then launched a big final push to resolve Greece's bailout woes. European Union president Herman Van Rompuy called for a new deal with Athens "by the end of the week" on the conditions underpinning the long-delayed second bailout for Greece. US stocks recouped most of their early losses Monday, showing resilience despite Greece's stalled bid to obtain a crucial debt writedown from private creditors to avoid default. The Dow Jones Industrial Average slipped 0.05 percent to finish at 12,653.72 and the tech-heavy Nasdaq dropped 0.16 percent to 2,811.94.