* U.S. ambassador says Karzai has 'much to do'
* Karzai plans to raise issue of civilian casualties
* U.S. general promises big effort to reduce deaths (Adds details on casualties, Senator Franken comments)
By Sue Pleming
WASHINGTON, May 10 (Reuters) - Afghan President Hamid Karzai began a trip to Washington on Monday, planning to press the Obama administration hard on civilian casualties and facing renewed pressure on weak governance and corruption.
Karzai spokesman Waheed Omer predicted "frank" exchanges during the four-day trip, aimed at showing a united front after weeks of public bickering between the White House and the Afghan leader at a pivotal time in the nine-year war.
"However nice we can be, we will raise issues that we believe that if addressed jointly by Afghanistan and the United States will help us strengthen this partnership," Omer said at a briefing at Radio Free Europe/Radio Liberty in Washington.
High on the agenda for Wednesday's meeting with President Barack Obama will be Afghan concerns about civilian casualties, Omer said, as well as night raids.
Rising civilian casualties have undermined public support for the presence of U.S. and other foreign forces in the country. More than 2,400 Afghan civilians were killed in 2009, making it the deadliest year of the war. Many of those were killed by insurgents.
The Pentagon has acknowledged that NATO forces killed 49 civilians between October and March.
U.S. General Stanley McChrystal, who is in charge of U.S. and NATO forces in Afghanistan, said minimizing civilian casualties was key for his counterinsurgency strategy to work.
"Inside Afghanistan the importance of reducing those casualties to convince the Afghan people that we are here for their welfare is absolutely strategic and so we give it that level of effort," he told reporters at a White House briefing.
CORRUPTION ON AGENDA
U.S. ambassador to Afghanistan, Karl Eikenberry, who has been critical of Karzai in the past, said "increasing accountability" of the Afghan government was another important topic on the agenda, adding there were signs of progress.
"Ultimately though, the customer that has to be satisfied is the people of Afghanistan," Eikenberry said. "Much has to be done," he added, in tackling corruption and better governance.
Omer defended his government's efforts. "Corruption is not only something connected to the Afghan government," he said.
Karzai incensed the Obama administration and Congress in recent months by blaming much of the corruption on Western donors, who he said also were responsible for some of the election fraud in last year's flawed poll.
Eikenberry said every relationship experienced "ups and downs" and Obama had full confidence in Karzai, who will get the red carpet treatment during his visit.
"What measures true partnership is the ability when the stakes are as high as they are for Afghanistan and the United States of America to be able to work our way through difficulties and come back together," said the ambassador.
But in private, the message from Obama is expected to be firm -- that Washington wants to start pulling out U.S. troops from Afghanistan in July 2011 and Karzai must do a better job if he wants to sustain U.S. public support for the war.
A Washington Post and ABC News poll on Sunday showed 52 percent of Americans think it is not a war worth fighting for the United States, which invaded Afghanistan to oust al Qaeda and the Taliban after the Sept. 11, 2001, attacks.
Karzai is expected to get some heat from Capitol Hill, where pressure is growing for Afghans to take more responsibility both militarily and in rebuilding the country.
Democratic Senator Al Franken said when he was in Afghanistan in January, he saw more U.S. State Department officials willing to rebuild the country than Afghans.
"I kept wondering where are the Afghan officials from Kabul, out in the field with their American international counterparts, just as the Afghan soldiers are partnering with international forces?" Franken said.
Karzai's visit comes at an important juncture in the war, with 30,000 additional U.S. troops expected there by the end of August and an upcoming military offensive to take full control of Kandahar, the spiritual hub of the Taliban in the south.
Karzai is expected to push for more equipment and help for training Afghan security forces. He also probably will discuss a growing worry among many Afghans that U.S. commitment to the country will wane quickly once it starts withdrawing troops.
More immediately, there will be a so-called grand council of Afghans, or peace "jirga," due to start in Kabul on May 29 to discuss how to make peace with the insurgents. (Additional reporting by Steve Holland, Ross Colvin and Susan Cornwell; editing by Mohammad Zargham)