Senator Joseph R. Biden on a visit to Ramadi, Iraq.

By MICHAEL R. GORDON

WASHINGTON - In three decades in Washington, Senator Joseph R. Biden Jr. has been one of the Democratic Party’s most energetic leaders on foreign policy.
Should he be elected vice president on the Democratic ticket with Senator Barack Obama, Mr. Biden would be advising a president who would take office with slim credentials in foreign affairs .
Both Mr. Biden and Mr. Obama fit into the mainstream of Democratic thinking on foreign policy and national security, which emphasizes working with allies and using force as a final recourse.
Mr. Obama opposed the war in Iraq from the beginning, staking out a position against it while still a state legislator in Illinois. Mr. Biden took a different approach to Iraq from Mr. Obama’s; Mr. Biden called for governing power in Iraq to be decentralized among three largely autonomous Sunni, Shiite and Kurdish regions.
But like Mr. Obama, Mr. Biden has for several years opposed the administration’s handling of the war, especially Mr. Bush’s decision to send additional troops - an administration strategy that military experts say has helped to reduce violence in Iraq.
Mr. Biden is widely seen as a liberal- minded internationalist. He has emphasized the need for diplomacy but has been prepared to back it with the threat of force. An early advocate of military action to quell the ethnic fighting in the Balkans, he has not been averse to American military intervention abroad.
He has been loath to give the United Nations a veto over American policy decisions. But he has also sought to ensure that the United States acted in concert with other nations.
As chairman of the Senate Foreign Relations Committee, Mr. Biden has presided over more than 50 hearings since January 2007.
He oversaw many more during his three previous stints as chairman of the panel’s subcommittee on European affairs.
As Yugoslavia started to come apart in the early 1990s, Mr. Biden urged American intervention to stop ethnic cleansing of Muslims in Bosnia. He was among the first to advocate lifting the arms embargo on the Bosnian Muslims and supporting them with NATO air power.
That policy was opposed by President George Bush and, initially, by President Bill Clinton . But it became the basis of a new policy that was eventually followed by a successful NATO peacekeeping effort.
No issue has gotten more political scrutiny, however, than Mr. Biden’s position on Iraq.
Mr. Biden’s appears to have shifted closer to the policy Mr. Obama advocates. He has emphasized the need to withdraw all combat brigades within 16 months of taking office, while building up troops in Afghanistan. There is much in their positions that remains to be spelled out.