WASHINGTON (Reuters) - A bipartisan group of U.S. members of Congress has backed a proposal for $7.5 billion of new military funding for U.S. forces and their allies in the Asia-Pacific region, where tensions have risen over China’s territorial ambitions and military buildup.

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Five members of the U.S. House of Representatives and eight senators from both the Democratic and Republican parties wrote to Defense Secretary Jim Mattis to support the Asia-Pacific Stability Initiative (ASPI) proposed in January by John McCain, chair of the Senate Armed Service Committee.

Copies of the letters were seen by Reuters. Their signatories include members of the armed services committees in both houses of Congress.

McCain’s proposal calls for $1.5 billion annually for five years to 2022 to boost U.S. munitions stocks in the region, build new military infrastructure, such as runways, and help allies and partners increase their capabilities.

The House letter urged Mattis to incorporate McCain’s proposal in the fiscal 2018-22 defense budgets.

“The Asia-Pacific region holds many interests for U.S. foreign policy that will require our government to continue to prioritize our time, energy and resources there,” it said.

The letter called former President Barack Obama’s policy of giving precedence to the Asia-Pacific “sound” and it was “critical” that this be continued under President Donald Trump.

It expressed concern about “the eroding military and economic balance that is the result of the People’s Republic of China’s two-decade military modernization, combined with the effect of years of sequestration on the U.S. military and our foreign policy apparatus.”

The Senate letter also expressed concern about increasing Russian activity in the region and North Korea’s nuclear and missile programs.

“ASPI will show both allies and adversaries that the U.S. remains committed to ensuring peace and security in a region that contains the world’s three largest economies, four most populous countries, six of the world’s largest armies, and five of the seven U.S. mutual defense agreements,” it said.

Trump has vowed to take a tougher line with China and to build up the U.S. military, although it is unclear whether he will succeed in lifting caps on defense spending that have been part of “sequestration” legislation.

China is due to announce its defense budget for this year this weekend, and its navy is likely to secure significant new funding as Beijing seeks to check U.S. dominance of the high seas and step up its projection of global power.