BERLIN (AP) — 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 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.

Merkel, 55, has been a leading European advocate of strong action to combat climate change, legislation on which is only slowly making its way through the U.S. Congress.

Berlin is lukewarm at best about Muslim Turkey's bid for membership of the European Union; Washington is a strong supporter of Turkey's EU aspirations.

At home, Merkel's capable but cautious leadership has earned her consistently high popularity ratings since 2005. She prefers to listen and consider before acting.

Germany's election in September strengthened her, allowing her to dump a "grand coalition" with the center-left Social Democrats, Germany's second-biggest party.

She has switched to a new alliance with the pro-business Free Democrats that aims to spur growth in Germany, Europe's biggest economy, in part through future tax cuts, but will face a stronger opposition in parliament.

Merkel is the daughter of a Protestant pastor who moved his family to the east when she was very young. She told Congress Tuesday that America "was simply unreachable to me" until the Berlin Wall fell in 1989.

"The wall, barbed wire and orders to shoot limited my access to the free world," she said, adding that films and books smuggled in by relatives from the west helped form her picture of the U.S.

"I was enthusiastic for the American dream — the opportunity for everyone to be successful, to become something through their own efforts," she added. Merkel said she flew to the U.S. for the first time in 1990.

Merkel, who was working as a scientist when the Berlin Wall fell, entered politics in her mid-30s as communism crumbled.

"I really enjoyed being a physicist," Merkel said recently. "But after the wall fell, politics became my passion."

She got involved in a new political group, Democratic Awakening, and became a spokeswoman in 1990 for East Germany's first and only democratically elected government.

Later that year, she was elected to reunified Germany's parliament for the party of then-Chancellor Helmut Kohl, who swiftly put her in his Cabinet.