The United States intends to complete its mission in Iraq and will not allow the country to become a staging ground for attacks on Americans, U.S. Vice President Dick Cheney said on Tuesday.

"All Americans can be certain that we intend to complete the mission so that another generation of Americans does not have to come back here and do it again," Cheney told about 3,000 U.S. troops at Balad Air Base 70 km (45 miles) north of Baghdad.

The war in Iraq, which enters its sixth year this week, is deeply unpopular in the United States and has contributed to President George W. Bush's low popularity ratings. It is a major issue in the November U.S. presidential election.

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Democratic presidential candidates Hillary Clinton and Barack Obama are campaigning to bring U.S. troops home while the presumptive Republican candidate, John McCain, supports keeping high numbers of troops in Iraq until it is more stable.

Cheney, who arrived in Oman after visiting Iraq to assess the success of a U.S. troop build-up, on Monday called the 2003 U.S.-led invasion of Iraq a "successful endeavor" and promised Iraqi Prime Minister Nuri al-Maliki unwavering U.S. support.

"We have no intention of abandoning our friends or allowing this country of 170,000 sq km to become a staging ground for further attacks against Americans," Cheney, an architect of the 2003 invasion, told the soldiers at Balad.

The Bush administration has said that leaving Iraq too soon would undercut security gains and allow al Qaeda militants there to regroup, potentially posing a future threat to the United States.