By Steve Holland

WASHINGTON (Reuters) - Beset by challenges at home, President Donald Trump on Friday embarks on the longest trip to Asia by an American president in more than a quarter century, looking for help to pressure North Korea to stand down from a nuclear crisis.

Trump's tour of Japan, South Korea, China, Vietnam and the Philippines from Friday to Nov. 14 will take him out of Washington as is preoccupied with several issues.

These include an intensifying federal investigation into Russian meddling in last year's election, New York's recovery from an attack that killed eight people and debate over a tax-cut plan that if approved by Congress would be his first major legislative victory.

The trip comes just days after Trump's former campaign manager, Paul Manafort, was indicted in the investigation into Russian meddling in the 2016 presidential election. His attorney general, Jeff Sessions, face Democratic calls to appear before Congress again to clarify his previous testimony about the campaign's Russia contacts.

Amid the furor caused by the revelations, the Kremlin said on Friday a meeting between Trump and Russian President Vladimir Putin was being discussed and Trump said it might happen.

"We may have a meeting with Putin. And, again – Putin is very important because they can help us with North Korea. They can help us with Syria. We have to talk about Ukraine."

Court documents made public on Monday also disclosed a Trump campaign foreign policy adviser, George Papadopoulos, pleaded guilty last month to lying to the FBI. They cited a March 2016 meeting, attended by Trump and Sessions, in which Papadopoulos offered to help arrange a meeting between candidate Trump and Putin.

While tweeting about developments vigorously this week, Trump told The New York Times on Wednesday that he was "not angry at anybody" over the case and there was nothing to suggest any collusion by his campaign and Russia.

Trump's extended absence has alarmed allies who, after seeing a healthcare reform bid fizzle, worry the tax effort could suffer without him at close hand to keep momentum going.

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The last time a U.S. president was in Asia for so long was in late 1991 and early 1992, when President George H.W. Bush became ill at a Japanese state dinner.

Trump will fly on Friday morning to Hawaii, stopping for a briefing on U.S. military forces in the Pacific and a visit to Pearl Harbor.

Trump will then visit Japan and South Korea in search of a united front against North Korea before going to Beijing, where he will push Chinese President Xi Jinping to get tougher with Pyongyang.

Trump will attend the Asia-Pacific Economic Cooperation summit in Danang, Vietnam, make a state visit to Hanoi and end his trip with the Association of South East Asia Nations summit in Manila.

(Reporting By Steve Holland; Editing by Cynthia Osterman and Chizu Nomiyama)