U.S. State Secretary Hillary Clinton's upcoming visit to Asia sends a strong message of engagement by the Obama administration in the region, a U.S. senior diplomat said on Tuesday.

Kurt Campbell, Assistant Secretary of State in charge of Asian and Pacific affairs, said Clinton's two-week visit, the sixth one in her tenure, is "complicated" and "lengthy".

Campbell said Clinton's visit, which starts on Wednesday, underscores Obama administration's emphasis on Asia on a range of issues, including strategic, political, multilateral, economic and trade.

The Obama administration, since it took office in Jan. 2009, has been stepping up efforts to engage Asia, especially Southeast Asia, both in bilateral and multilateral levels. Experts believed the efforts are meant to restore the level of U.S. influence in the region which had been ignored by his predecessor.

Campbell said Clinton's first stop will be Hawaii, where she will meet with commanders of U.S. forces in the Pacific. Clinton will also meet with Japanese Foreign Minister Seiji Maehara for a "substantial, intense interaction" on recent security developments and economic and trade issues.

Then, Clinton will go to Hanoi, capital of Vietnam, to be present at the East Asia Summit as a special representative of the U.S. President Barack Obama, said Campbell.

The United States will become a formal member of the East Asia Summit next year, and President Obama has announced that he will attend the summit next year in Jakarta, Indonesia.

After Vietnam, Clinton will also visit Cambodia, Malaysia, Papua New Guinea, New Zealand and Australia.

Besides Clinton's lengthy trip, Obama will visit India, Indonesia, South Korea and Japan next month.