Moldova's rebel region of Transdnestr said Monday that it was ready to host Russian tactical missiles if the Kremlin were to ask, escalating growing tensions about defense between Moscow and Washington.

Transdnestr linked the offer to the possible deployment of U.S. interceptor missiles to neighboring Romania. Both Romania and Bulgaria have offered to host elements of a reconfigured U.S. missile shield.

Prime Minister Vladimir Putin and other officials have called U.S. missile defense plans an obstacle to a successor to the 1991 START nuclear arms reduction pact, under negotiation for months.

Transdnestr's leader, Igor Smirnov, said he was prepared to host Russian missiles and made clear that the offer was linked to the latest U.S. missile plans.

"As far as the Iskander [missile] is concerned, we have long said we are ready," he said, Interfax reported.

The breakaway region's offer came a day after Foreign Minister Sergei Lavrov said Moscow's ambassador to Washington had raised the missile issue, RIA-Novosti reported.

"We have already asked our partners in Washington … what does this all mean and why after the Romanian 'surprise' there is a Bulgarian 'surprise' now," Lavrov was quoted by RIA-Novosti as saying in Nicaragua.

This month, the NATO and European Union member Romania, which borders Moldova, said it would accept U.S. interceptor missiles under a reconfigured plan. On Feb. 12, Bulgaria expressed its readiness to play a role.

The revised anti-missile system crosses one of the red lines — along with NATO membership for Ukraine and Georgia — that Moscow drew as conditions of its agreement to reset U.S. relations, said Masha Lipman, an analyst at the Carnegie Moscow Center.

"Now Romania and Bulgaria are an issue. This further nurtures the distrust on the Russian side — the notion that the U.S. is not seeking to build relations with Russia and develop a constructive dialogue but is pursuing its own goals regardless," Lipman said.