BERLIN— Angela Merkel, the first leader of reunited Germany to grow up under communist rule, has worked as chancellor to warm up ties with the United States _ a country she couldn't travel to until she was in her mid-30s.

The former East German physicist, also the first woman to lead her country, restored cordiality to ties strained over theIraq former East German physicist, also the first woman to lead her country, restored cordiality to ties strained over the Iraq war while firmly but diplomatically acknowledging political differences.

The conservative's address to Congress Tuesday came weeks after she won a new four-year term at the head of a new center-right coalition.

That triumph further cements her status _ awarded by Forbes magazine four years running _ as the world's most powerful woman.

When she came to power in 2005, Merkel inherited chilly relations with the administration of George W. Bush, who was irked by predecessor Gerhard Schroeder's strident criticism of the Iraq invasion.

Merkel worked hard on friendly ties with Bush, earning an invitation to his Texas ranch in 2007. But she also showed that she is no pushover, winning respect by publicly criticizing the Guantanamo Bay detention center.

She has built up a solid working relationship with President Barack Obama, seen by many in Germany as a fellow pragmatist.

Merkel has praised the United States' contribution to making her country "reunited, a partner in Europe and in the trans-Atlantic community."

She says she enjoys "close cooperation" with Obama and that Germany is a "reliable and intensive partner" for America, with which it works closely on issues such as Iran's nuclear program.

Still, there is potential for tension. Germany has some 4,000 troops in the NATO mission in Afghanistan, which is unpopular at home. A parliamentary mandate allows for a maximum of 4,500 soldiers, and that appears unlikely to increase in the near future.