BAGHDAD — Barack Obama began today his first on-the-ground inspection of Iraq since launching his bid for the White House, with U.S. commanders ready to brief him on progress in a war he long opposed and Iraqi leaders wanting more details of his proposals for troop withdrawals.

His stops in Baghdad — and other areas of the country — marked the second major leg of a war zone tour that opened in Afghanistan. The contrasts in tone and message were distinct.

Obama sees the battle against the resurgent Taliban and al-Qaida in Afghanistan as America's most crucial fight and supports expanding troop strength to counter a sharp rise in attacks.

But Obama had stood against the Iraq invasion and now worries that an open-ended U.S. combat mission will sap military resources and focus — at a time when Iraq violence has dropped to its lowest level in four years.

The Illinois senator — traveling in a congressional delegation with Sens. Jack Reed, D-R.I., and Chuck Hagel, R-Neb. — arrived in the country early Monday. Their first stop was Basra, the U.S. Embassy said.

Basra is the center for about 4,000 British troops involved mostly in training Iraqi forces. An Iraqi-led offensive begun in March reclaimed control of most of the city from Shiite militia believed linked to Iran.

Travel plans for the Democratic presidential candidate were kept secret, but he was seen arriving for a meeting with Prime Minister Nouri al-Maliki in the heavily protected Green Zone.

Obama has made no public statements since arriving in Iraq. There was no noticeable tightening of security on Baghdad's streets and inside the Green Zone.

The meetings were expected to include the top U.S. commander in Iraq, Gen. David Petraeus, and other military chiefs outlining the significant gains in recent months against both Shiite militia and Sunni insurgents including al-Qaida in Iraq.

The White House and military leaders — and many residents of Baghdad — trace the momentum back to last year's buildup of more than 30,000 troops in areas around Iraq's capital. Obama's challenger, Sen. John McCain, has tried to hammer Obama on his critical remarks before the so-called "surge."

In an interview Monday on ABC's "Good Morning America," McCain said he hoped Obama would now "have the opportunity to see the success of the surge."

"This is the same strategy that he voted against, railed against," McCain said. "He was wrong about the surge. It is succeeding and we are winning."

All five surge brigades have left Iraq, but there are still about 147,000 U.S. soldiers in Iraq, more than in early 2007.

Obama has endorsed removing U.S. combat forces over a 16-month period, but has been less precise on the size and type of U.S. military role needed in Iraq after an exit from the battlefield.

Iraqi leaders are expected to press Obama for more clarity on his long-term vision. Such discussions have added importance since Iraq and U.S. negotiators appear stalled in efforts to reach a long-range pact to define future U.S. military presence and obligations.

American diplomats hoped to reach a final accord by the end of the month, but it now seems the goal is a stopgap "bridge" document that would maintain the status for U.S. forces once a U.N. mandate on their presence expires at the end of the year. Such as move would leave the hard bargaining to the next president.

Iraqi leaders, meanwhile, have gained a new measure of self assurance with revenue from record high oil prices and Iraqi-led successes to hobble Shiite militias believed linked to Iran. Recently, Iraqi leaders have increasing pressure for some kind of timetable for U.S. troop withdrawals.

Last week, the White House agreed to work on a "general time horizon" for removing U.S. troops — a significant reversal from President Bush's longheld opposition to discuss any timeframes.

Obama is likely to face more questions about his pullout plans from al-Maliki.

Al-Maliki was quoted last week by a German magazine appearing to endorse Obama's 16-month timetable. The Iraqi leader's aides have since said his remarks were misunderstood, and he is not taking sides in the U.S. election. Obama also is expected to meet Iraqi President Jalal Talabani.

It was unclear whether Obama would make any public appearances or comments while in Iraq. But even a low-key visit may garner more scrutiny than any stage of his overseas trip, which is scheduled to move on to Jordan, Israel and European capitals.

Iraq is one of the lighting rods in the presidential showdown with McCain.

McCain has been critical of Obama's position on Iraq, saying the decision to pull out should be determined by progress, not a timetable. McCain also strongly backed the troop surge into Iraq last year.

McCain's foreign policy adviser, Randy Scheunemann, said Obama "is stubbornly adhering to an unconditional withdrawal that places politics above the advice of our military commanders, the success of our troops, and the security of the American people."

There is no question that Iraq is a significantly different place than during Obama's first visit in January 2006, when the country was caught in a growing Sunni insurgency and was moving toward a flood of Sunni-Shiite violence.

Militant attacks and targeted killings by sectarian death squads is sharply down — by many measures back to levels before the rise of the Sunni insurgency in 2004.

So far this month, the U.S. military has reported nine soldier deaths in Iraq, in addition to the discovery of two bodies of soldiers abducted last year. The lowest monthly toll of the war was this May, when 19 military deaths were reported.

In Afghanistan, meanwhile, U.S. military officials say the number of attacks in eastern regions, where most of the foreign troops are American, has increased by 40 percent so far in 2008 compared with the same period in 2007.

But there are pockets of concern in Iraq.

Bombings and slayings have been creeping higher in the northern city of Mosul, the last main urban stronghold for al-Qaida in Iraq. Insurgents also remain entrenched in the Diyala Province northeast of Baghdad and a main gateway to the city. Iraqi authorities have announced plans to send more forces into the area.

Iraqi leaders also continue to stumble on some political measures supported by Washington.

The nation's election commission on Sunday proposed delaying important provincial elections from this October until near the end of the year. Iraq's parliament has been unable to reach agreement on the guidelines for the voting, which would hand greater powers to regional authorities and is seen as a vital step toward national reconciliation.

Obama arrived following a brief stop in Kuwait, a key U.S. ally. The delegation met Sunday with the emir, Sheik Sabah Al Ahmed Al Sabah, and other senior officials, the Kuwait News Agency reported.

In Afghanistan, Obama met with U.S. military commanders and troops and held talks with President Hamid Karzai.