WASHINGTON (AP) — Republican John McCain again insisted victory in Iraq “is finally in sight.” So why, asked Democrat Barack Obama, does his presidential opponent still oppose a timetable for withdrawing American forces.

The argument over the unpopular war — a key issue separating the candidates — flared again Monday after McCain spoke to the Veterans of Foreign Wars convention, a friendly audience given his service as a Navy fighter pilot and prisoner of war in North Vietnam.

Overshadowing the back and forth this week is the mounting speculation about who Obama will choose to be his vice presidential running mate. An announcement is expected within days. Obama is believed to have narrowed the field to Virginia Gov. Tim Kaine, Delaware Sen. Joe Biden, Indiana Sen. Evan Bayh and Kansas Gov. Kathleen Sebelius. His vanquished rival, New York Sen. Hillary Rodham Clinton, also remained a possibility.

The Iraq war, the top election issue before the presidential contest began, has given way to voter concerns over a stumbling economy that shows no signs of rebounding as Democrats head into their national convention next week. Republicans gather to nominate McCain the following week.

McCain, a four-term Arizona senator, said the victory he envisioned still could be “squandered by hasty withdrawal and arbitrary timelines. And this is one of many problems in the shifting positions of my opponent, Sen. Obama.”