"If we lose Doklam, there is every possibility that we may lose the northeastern states to China," he told a press conference here.
Kumar, a former parliamentarian from the steel city, also asked the Centre to win back the confidence of "its old friends, like Russia, to face China strongly."
Asked about China's threat to launch a limited war to drive out Indian forces from Doklam, he said, "A face-off between India and China has never happened in the Sikkim sector. The sector is important for our national security".
"The government has itself admitted that China had entered into our territory 240 times last year but did not take any step to check it," he said.
The UPA government had proposed to raise Mountain Division force at a cost of Rs 60,000 crore in 2013-14 and had even released around Rs 7,000 crore to Rs 8,000 crore for the purpose but the NDA dispensation has cancelled the proposal, Kumar claimed.
Appreciating the country's stand over the Doklam issue, he supported the Modi government's stand and urged political parties to remain united on the face-off issue to give a "befitting reply" to China.
"We should exhibit unity to push China back," he said.
Kumar said attacked the BJP leadership of making an issue over AICC Vice-president Rahul Gandhi meeting the Chinese ambassador amidst the border face off in Sikkim, saying "its senior leaders have been visiting China frequently".
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)