WASHINGTON (BLOOMBERG) - The Biden administration is lobbying Democratic senators to put the brakes on a Bill that would alter US policy towards Taiwan, including by designating it as a major non-Nato ally, according to people familiar with the matter.

The legislation also would provide Taiwan with US$4.5 billion (S$6.2 billion) in security aid and support its participation in international organisations.

It is sponsored by Senate foreign relations chair Bob Menendez, a New Jersey Democrat, and Republican Lindsey Graham of South Carolina, both harsh critics of China, which considers the self-governing island of Taiwan as part of its territory.

"The White House has significant concerns," said Senator Chris Murphy, a Democrat from Connecticut and member of the Senate foreign relations committee. "I have significant concerns."

Mr Murphy said the committee is delaying work on the legislation until September, and it may be rewritten.

The committee had planned to vote on the Bill Wednesday (Aug 3).

Fallout

The US has treated Taiwan as a major non-Nato ally since the George W. Bush administration. The Bill will formalise that designation.

The administration is already trying to deal with increasing US-China friction, which was exacerbated by House Speaker Nancy Pelosi's visit to Taiwan this week.

Taiwan was a major topic of a call last week between US President Joe Biden and Chinese President Xi Jinping.

Mr Menendez, in an op-ed published Wednesday in the New York Times, said the US strategy must be geared to "deter and constrain Beijing's problematic behaviour".

"As China challenges us across every dimension of national security - militarily, economically and diplomatically and on values - we are laying out a new vision that ensures our country is positioned to defend Taiwan for decades to come," he wrote.

Mr Graham rebuked the White House for trying to stymie the Bill.

"It's a miscalculation of how to keep the world in order. At every turn, they take the weakest path," he said. "If you put this on the floor of the Senate, it would pass overwhelmingly."

Reservations

National Security Council spokeswoman Adrienne Watson said the Bill could improve cooperation and coordination with Taiwan, but she confirmed the White House's reservations on certain aspects, particularly as it addresses the US' "one China" policy that deems the question of sovereignty over Taiwan as undetermined.

"We do have concerns with elements of this Bill which would contradict and undermine the United States government's longstanding one China policy and contravene the president's constitutional authorities to determine the United States' position on the status of Taiwan and to determine the manner of diplomatic communications with representatives of Taiwan," Ms Watson said in an e-mailed statement.

The Biden administration considers the legislation counterproductive, and that it will interfere with the decades-old approach of "strategic ambiguity" about whether the US military will defend Taiwan against communist forces.

"I'm not sure this is the moment to throw out 40 years of policy," Mr Murphy said, while adding that "it makes sense for us to draw closer to Taiwan".